Camming a VTS

[pug205gti87]

hi there i am getting a vts in the next few weeks. i am planning on camming it with catcam 708's and all the usual bits. what is a cammed vts like to drive. can you feel more of a difference to like a non cammed one.? i jst want some feedback before i spend about 900 quid on cams and a remap? thanks

[bullit]

yes theres a good difference. on a vts for price and performance nothing can beat it before going the next step and spending alot of money

[pug205gti87]

o right so do you get more of a pull from 4000rpm onwards?

[KamRacing]

basically if you think of the current characteristics of the engine and enhance them more. ie more of a push at higher rpm vs the lower revs.

not so much so that its suffers day to day with the 708s though

[pug205gti87]

wat will it be like against standard vts's at say santa pod if i am running bout 154bhp?

[bullit]

wat will it be like against standard vts's at say santa pod if i am running bout 154bhp?

you should beat it by about a second

[AliC]

Sounds good m8, keep it posted if you do decide to cam it! All the best

[spencer_cammedvts]

driving is a little pokey in the lower revs but the car pulls a damn lot harder and you can wipe smug smile of the faces of people that own civic type r's and clio sports ;)

[Ry_B]

Yer but then they laugh at you when your car falls apart lol

I think above 80 the Type R would still have the edge

[spencer_cammedvts]

THINK AGAIN MATE. they dont at all!

[samcook]

what does yours go like spencer, as i never got a drive of it last time :(! should be getting mine done soon tho

[jeeves_101]

i want mine cammed at some point in the new year too.

go like stink don't they?

[spencer_cammedvts]

i might be selling mine yet. i can either see a nice EK9 coming my way or a turbo for the vts.

[L8R_VTR]

Turbo it mate!!!!:y:

[Toad]

I know I've got an S1 box installed, but trust me, in 5th gear, it will pull from 85 to 125 very damn quickly.

[spencer_cammedvts]

thanks toad ;) people who have never driven a cammed vts on their own just dont understand the types of car they can keep with.

[Toad]

Yeah man. If you can drive it correctly, it certainly goes!

[samcook]

arrgh need my cams in lol

[Finchowned]

My standard VTS was giving my friends 172 Cup a hard time on the dual carriageway so I can only imagine what a cammed VTS would be like :D

[spencer_cammedvts]

you certainly do sam!

[jablitt]

i love the sound of a cammed saxo, the lumpy engine noise on idle is music to my ears!

[ToRn]

My AX VTS had cams and it abliterated Type R's but then again its a lot lighter than a Saxo.

[spencer_cammedvts]

dont wory mate. mines stripped lol. only way forward!

Guuted though. went home at dinnertime and when i started her up again, my head gasket blew. white smoke coming from the exhaust big time! parts are allready on there way and its another excuse to get her skimmed and up the compression a bit more ;) might flow my inlet mani a bit better too :)

[Toad]

Wasn't that headgasket quite new???

[spencer_cammedvts]

10 months old mate. is that really bad that its gone? am i doing something wrong?

[williamsvts]

no way should it go that quickly. maybe a few years of hard use but not ten months!!!

[Joesnow]

10 months old mate. is that really bad that its gone? am i doing something wrong?

Did you get the head skimmed when it went last time?

[Toad]

Did you put it on yourself?

[spencer_cammedvts]

yer i put it on myself. iv done everything myself bar the remap. its one of the water chanels thats broken through to one of the cylinders. so al least i aint got to flush everything. obviously it makes sense to do an oil & filter change now. but i dont know what i was doing wrong. i had 12 thou skimmed off last time so compression was up a bit. dont think that would make all that much off a difference though! ill get it skimmed again but not really sure how much to take off to be safe. probably just get 4 thou taken off to be safe. as iv got the 708's in aswell. what do you lot recon?

[Joesnow]

I’d make sure you get it completely flat or the headgasket will just keep going… you could take it to a specialist to get it measured up properly to see exactly how much needs taking off… then work out how much clearance you have with the 708s and if there’s enough clearance you could increase the compression ratio a bit. You will probably have to use a thicker gasket to stop the valves clashing if you take too much off

[spencer_cammedvts]

i cant remember what the clearence is with standard head fitted with 708's. can anyone enlighten me? how much clearance do you want ideally?

[Joesnow]

Think it would be a pain in the arse to work out as it would depend on the cam timing as well… if it wasn’t clashing with 12thou skimmed off you could just take off what you need so that its completely flat and get a thicker headgasket to match… so say you take 6tho off just get a headgasket + 6thou? Then you know for sure it won’t clash.

[spencer_cammedvts]

i think its justy over 1mm clearence at the mo so i think ill be safe to take off another6though. (0.15mm)

well soon see!

[dan-iow]

i have a 106 gti and would like to get it cammed. which cams is it you can fit without needing a remap?? and what are the gains like with these??

reason i ask is i live on the isle of wight and there is really anywhere to get a remap :(

[spencer_cammedvts]

you can fit any cams without mapping but you car will run really bad and you will only gain about 2bhp from them you have to get them mapped really if yuo want to see any gains. get over here and get it mapped. you wont regret it ;)

[dan-iow]

yeah thats kl, but i mean im going to have to fit the cams the drive all the way to get it mapped with the car running like a bag of poo.

[Paul_Collins]

put cams in mine a month or 2 back, and you do supprise ppl, especially with a s1 box :p

[d4r3n]

does camming the vts really make alot of diffrence then ??

[samcook]

does camming the vts really make alot of diffrence then ??

well wot do you think 120bhp to around 150/160bhp

[d4r3n]

more then likly feal the diffrence then lol whats it like in relation to speed does the top end get any better or well after the 100 mark ?

[Paul_Collins]

pulls better through every gear, and with a s1 box its rediculous.

[d4r3n]

nice lol how much u talking for the s1 box ??

[OLLYVTS]

What would a cammed vts with 708s do 0-60 in(roughy)

[Jazz]

What would a cammed vts with 708s do 0-60 in(roughy)

Good q mate, a smidge under the 7 mark I'd imagine? Also depends on wheel, suspension set up and how much traction they can get off the mark. My standard VTS has traction issues off the mark with std wheels and good tyres, i can only imagine what a cammed version would be like... but yeah, the look on Type-R owner's faces when the wee Saxo is sitting on their arse would be priceless. :P

[OLLYVTS]

I was thinking it must be just below 7 as i have heard they will keep up with type R's.

[Jazz]

Only thing is, the cammed VTS in question will most likely have a host of other mods done to it... i don't think theres a silly enough VTS owner thats going to just pop in 708s and a map and say, 'ahh there we go, lets go butch some Type-Rs!' They are going to have (more than likely) full exhaust system, induction, and most probably different wheels and suspension, all of which will affect acceleration time. Bearing that in mind, I wouldn't be surprised if a cammed VTS did the sprint in dry conditions, with good tyres and got around the 6.5ish mark. Quite possible if alls running smoothly.

Of course this is just an objective estimate, if anyone lucky enough to have a cammed VTS has gone and done a measurement, would be interesting to know...

[Ryan]

1. s1 boxes are rare as fuck, dont expect a good one for under £200

2. ive seen many run mid 6 to 60 on 708s, depens how shit you are at driving

[OLLYVTS]

Thats pretty good to know that they do 0-60 in around 6.5 seconds.Im thinking about get a set 708s and a remap after xmas.I have already got a manifold,de-cat pipe,magnex'cat back system and a induction kit.

Would there be anythink else you would buy before getting a set of cams and re-map?

[Ryan]

Thats pretty good to know that they do 0-60 in around 6.5 seconds.Im thinking about get a set 708s and a remap after xmas.I have already got a manifold,de-cat pipe,magnex'cat back system and a induction kit.

Would there be anythink else you would buy before getting a set of cams and re-map?


as said depends on driver.

ive killed a 708 set up vts in my vtr because the driver was a mong.

[OLLYVTS]

as said depends on driver.

ive killed a 708 set up vts in my vtr because the driver was a mong.

I totally agree with you about that it depends on the driver.Would you recomend i buy anythink else before i get 708s and a re-map?

[Ryan]

I totally agree with you about that it depends on the driver.Would you recomend i buy anythink else before i get 708s and a re-map?

depends how far ur gonna go on engine, if you plan TBs etc..

[d4r3n]

do they sound any diffrent through the rev range ???

[bullit]

yes...

[Steve]

Good q mate, a smidge under the 7 mark I'd imagine? Also depends on wheel, suspension set up and how much traction they can get off the mark. My standard VTS has traction issues off the mark with std wheels and good tyres, i can only imagine what a cammed version would be like... but yeah, the look on Type-R owner's faces when the wee Saxo is sitting on their arse would be priceless. :P

http://www.youtube.com/watch?v=Tk7BARqUw8U

love that video, not sure what that VTS running but it is a Type R ITs Racing

[spencer_cammedvts]

i can run between 6-6.2 seconds. it depends on a lot of things. weight of car, how you drive it and you definatly need a set of good tyres. preferably proxie TR1's

[k2thecsaxo]

http://www.youtube.com/watch?v=Tk7BARqUw8U

love that video, not sure what that VTS running but it is a Type R ITs Racing

quality that :y:

[Toad]

Under 6 for me, so there! haha :d

http://video.tinypic.com/player.php?v=67x172c

[thadogg]

That looks rapid toad mate!

[GroomGTI]

what diffrence would it make to cam a vtr then?

[Ry_B]

Some but easier to just whack the vts engine ni

[Ry_B]

Under 6 for me, so there! haha :d

http://video.tinypic.com/player.php?v=67x172c

Fook...! Can't wait till my gti comes :)

[GroomGTI]

what sort of bhp extra would you get m8?

[Paul_Collins]

picked my s1 box up for £180 but it needed new bearings and seals and new sync rows, but my mates a gearbox specialist so im getting it done for quite cheap.

[spencer_cammedvts]

tell the differnce a lot with the s1 box mate? also does it knock much off top end?

[Paul_Collins]

yes alot of difference compared to the VTS one. dont think it knocks much off top end. its very rapid through the gears. hard to stop it spinning.

[spencer_cammedvts]

osunds good to me! think thats next on my list of things to buy before the turbo comes ;)

[Ry_B]

Any places that sell recon s1 boxes? Or just have to wait around on forums till one pops up?

[Paul_Collins]

got mine from 106 rallye register, not gonna be cheap, also dont know what condition its gonna be in, when i got mine the guy said it was mint, and was better than the box in his car.

His box must have been shagged cos this one would crunch into second and was whining.

[Toad]

osunds good to me! think thats next on my list of things to buy before the turbo comes ;)

You won't want an S1 mate if you're going to charge your Saxo. The stock gearbox will be just fine.

[Paul_Collins]

was thinking that, s1 box would be too short for a turbo

[spencer_cammedvts]

i wont be charging it for about a year yet mate. im gonna be keeping the S box and then just swap them over again when the car comes off the road.

[Karl]

Sorry to be stupid,
but can someone post the link of all the gearboxes in a VTS (SSC i think it is)
......interested in camming mine around Summer.

[jeeves_101]

reading this makes me want cams now.

but i want some other bits and bobs first, but cams are on the list.

[Steve]

Sorry to be stupid,
but can someone post the link of all the gearboxes in a VTS (SSC i think it is)
......interested in camming mine around Summer.

i covered it on here have a search :y:
threads called "VTS gearbox speeds"

[Karl]

tyvm mate.

[jeeves_101]

am i correct in thinking that an S1 gearbox on a vts creates a slower top speed than the vts box?

also, is it possible to put a vts 5th gear on to stretch it out at all?!?!

[Karl]

yeah the s1 box will have a smaller terminal speed in 5th.

But that doesn't matter, unless you race autobahn..!

[Paul_Collins]

Yeah it is possible to put a vts 5th gear on a s1 box my mate was gonna do it to mine

[jeeves_101]

yeah, dont really need a massive top end, just the longer gear would make it better for motorway driving i think.

[Karl]

fair point,
but if your building some track slag mate, you want it to be quick.

Quick cars arent good on fuel.

[Gabbastard]

5th is the same on the VTS and S1 boxes. You need a VTR or Diesel 5th.

[jeeves_101]

5th is the same on the VTS and S1 boxes. You need a VTR or Diesel 5th.

oh right, how come there is the big difference in top end then?

is it the final drive thats different then?

[RICKYP-RPM]

oh right, how come there is the big difference in top end then?

is it the final drive thats different then?
yeah its the final drive it lowers the top end speed but gets you there quicker;)
i'm running a group n rallye box in my rallye and gti engine (same as vts) it tops out @ 125mph on the limitter in 5th but pulls like mad and gets there quite quickly;)

[jeeves_101]

yeah its the final drive it lowers the top end speed but gets you there quicker;)
i'm running a group n rallye box in my rallye and gti engine (same as vts) it tops out @ 125mph on the limitter in 5th but pulls like mad and gets there quite quickly;)

oh right cheers.

is that box similar to the S1 box?

[spencer_cammedvts]

TOAD what can you get out of yours mate? i usually sit at 80mph on the motorway what rpm are you at with the s1 box on mate?

[Toad]

I don't know if anyone will agree with me on this, but I have a feeling the ratios may be a tad different between the S1 and VTS stock box. The reason I think this, is because there seems to be a smaller rev drop when going from 3rd to 4th with the S1 than I remember with stock box.

The good thing with the S1 box is that it helps you keep the engine in its power band. As you can get through the gears quicker, you don't get so bogged down if you are a little low in the revs. For example, you can boot it from just under 4000 rpm in 2nd and it will spin the wheels, whereas before, it would bog down a bit.

[Toad]

TOAD what can you get out of yours mate? i usually sit at 80mph on the motorway what rpm are you at with the s1 box on mate?

Hmm, I would have to check to be certain mate. I think 80 mph would around 4500 - 4700 rpm in 5th at a guess?

[Toad]

I just like the way you can boot it from 85 ish in 5th, and the pickup is awesome. :y:

[Gabbastard]

Gear clusters are the same.

[Karl]

4,5 - 4,7 is really quite high for 80mph.

I think with my 1.1 box at 70 im at approx 3,3k.

[Toad]

The 1.1 box is just wrong... end of story.

[Toad]

Gear clusters are the same.

Fair enough. I still wonder why the rev drop seems less though...

[Karl]

The 1.1 box is just wrong... end of story.

Fair point, its not as bad as what people say,
when i get some $ I'll change it back to an S box or ph1 Rallye box.

[Steve]

Fair point, its not as bad as what people say,
when i get some $ I'll change it back to an S box or ph1 Rallye box.

what do you get out of your 1.1 top speed or all the way in 4th, still not sure if they sent me an s box or 1.1 :homme:

going to try get my blown vts box repaired, as got plenty spare boxes where can take the bell housings off and replace just need to see whats buggered internally :(

[Karl]

the SaxoSportsClub link in your thread earlier tells you what you can get in each gear...

its v similar to the VTS box in speeds.

[pug205gti87]

i cant believe the s1 box makes that much difference! that is amazing. your car is not on tbs is it toad?

[bullit]

no its not. 708s and BV head

[KamRacing]

I always thought that the 1.4 xsi gearbox had a pretty good set of ratios..

had a spreadsheet somewhere with them all plotted.

[bullit]

yeah it does. after s1 it is

[Gabbastard]

4.29 FD with sport cluster (3.417,1.95,1.36 etc) Shares 0.85 5th with VTS etc. You can get replacement 5ths from VTR or diesel boxes at 0.767, and if youre REALLY jammy you might find a 0.693 diesel 5th.

Some 1.1 boxes have 4.29 final drives btw, but have smaller planetary gears.

[Toad]

That vid was with the stock box. I can't quite hit 60 mph in 2nd anymore with the S1 box.

[Toad]

Spencer, I checked out the tachometer this evening. 80mph was 4675 rpm, there or there abouts. Not a bad guess before then! :d

[spencer_cammedvts]

thats 675rpm more than it is on the standard S box. doesnt sound to bad. where would be the best place to source a rallye box because iv been searching and there like rocking horse shit!

[Toad]

I wouldn't got to all the hassle if you are charging the car soon. I was lucky to find one from a breakers.

[spencer_cammedvts]

did it cost you much mate? wont be charging the car for at least a year yet mate. and will be keeping the s box in the garage.

[Jazz]

http://www.youtube.com/watch?v=Tk7BARqUw8U

love that video, not sure what that VTS running but it is a Type R ITs Racing

Awesome vid mate, loved it! But that Saxo was def not standard (my uncle's CTR comfortably pulls away from my VTS after an even first gear launch), but whatever set up the driver was running it did the job! Seemed to grip nicely off the line, not too much drama, just got on with it. Pulled cleanly from that Type-R, very very impressive... Right, time to get saving! :A:

[Toad]

did it cost you much mate? wont be charging the car for at least a year yet mate. and will be keeping the s box in the garage.

I think I paid the breakers £150 for it. It works fine, but I think it's on its last legs to be honest. Lot's of crunching going on, lol.

[pug205gti87]

lol mad stuff. so what have you got done to your car exactly have you had it rolling roaded lately?

[Toad]

It's been on loads of rolling roads. Lowest it made was 147 bhp and highest was 168 bhp.

It's just got 708 camshafts, and a fairly modified cylinder head.

[pug205gti87]

obviously all breathing stuff as well ye? how much can you get a big valve head for ? i could be interested in that

[rushy_23]

Bit of a range there eh Toad. Main thing is we all know it shifts.

[Toad]

obviously all breathing stuff as well ye? how much can you get a big valve head for ? i could be interested in that

Yeah, Scorpion full system, Supersprint mani and a Green filter enclosed in a fibreglass shell.

EDIT: The head was expensive. Somewhere around £700 I think. {gulp!} I paid even more to get it fitted properly.

[Toad]

Bit of a range there eh Toad. Main thing is we all know it shifts.

Yeah, very big range mate. I think the loss of weight is big contribution to the quick 0 - 60 time. As soon as I get the fibreglass bonnet on and the sunroof out, I'll get the car weighed up. Very interested to know where it's at!

[spencer_cammedvts]

iv nearly got mine back together now after the headgasket blow. just got to fit the cambelt and get her tensioned toninght, the bleed the coolant system. job done.

i took some pictures of my flowed head that i did myself. pics arnt very good but you can see the size of the ports etc which is the main thing.

[spencer_cammedvts]

ill gte them up when i get to work tomorra

[b0t13]

if i get a vts in jan, this is the route that im going to take, whats the advantages and info on a modified head, and is there any cheap performance options that could be done whilst the engine is apart when the cams are getting fitted?

[jeeves_101]

not really any cheap ways to do anything, unless you do the work yourself.
lightened fly may help abut, would free up the revs abit, but too light and torque will go, other than that, there isn't anything cheap thats good really.

[b0t13]

when camming the car, can u just by the cams themselfs or do u need the other parts aswell, like pulleys and stuff?

as cams alone are expensive and i dont want to buy the extra parts if there not needed, although i dont wonna cause engine wear if that happens without them.

[rushy_23]

VTS comes with venier pulleys im told. Hydraulic followers is another upgrade
with cams but dont think that essentual too. If it were me I would like to get
the belt changed while the timings being done but thats another not needed
expense.

but too light and torque will go

Is that true or is that something that somebodies just said in the past without
backing it up.
If the flywheel is L+B too much then wont it just be plain sh1t for the job full stop?

[b0t13]

ive heard that lightening the flywheel loses torque, apparently its true..

its sacrificing torque for bhp, so it depends on how u want the car to pull i suppose.

what about havin the head ported and polished? that expensive and are the gains good?

[Dibz]

The reason you lose torque when fitting a lightened flywheel is because your taking off rotational mass so altho the wheel will spin up faster it will also slow down and lose revs faster. Its all about the momentum the flywheel builds up when its full weight compraed to when it has been lightened. Dont let that put anyone off tho, its a great mod and makes the car feel so much more sporty!

[Ry_B]

Yeh bet it revs to fuck with a light flywheel

[Joesnow]

ive heard that lightening the flywheel loses torque, apparently its true..

its sacrificing torque for bhp, so it depends on how u want the car to pull i suppose.

what about havin the head ported and polished? that expensive and are the gains good?

don’t know exactly what you mean there… generally if you lose torque you will lose bhp as they are directly related…

think the only effects of a cheap flywheel will be a worse idle and it will pick up quicker in neutral and maybe a bit in 1st… a properly lightened and balaced flywheel isnt a chaep mod. I had a good look into this a while ago…

Think its only really worth while if it’s a race spec engine with a high rev limit where a decent idle isnt the main priority… it would also help reduce inertia loadings through the trnasmission on downshifts with a race spec box and clutch… and then lightening the standard flywheel wont give that much benefits, you really need to buy a new one… and they don’t come cheap

[Colin]

L and B flywheels just help the engine spin up the revs quicker. Thats all.

Better modification than bolting on a gay air filter or shite exhaust.

[Gabbastard]

My word.

You do not lose torque by lightening a flywheel.

[Joesnow]

You might think its lost torque because it’s more difficult to pull away… it’s really the inertia that’s been lost… one of the main reasons the flywheels there… I’m just trying to find a pic of a smashed one.

[Steve]

this has turned out to be a really good thread imo

[RedB]

Great info on tap so far...

[Colin]

My word.

You do not lose torque by lightening a flywheel.

yes, no is torque lost. A I said, just helps engine spin up quicker.

[Joesnow]

Right… the flywheels there for 2 reasons:


To store energy to keep the engine running smoothly at low rpms

To hold the clutch and provide a surface for the clutch plate to mate with… this means that it’s a stressed component… the torque from the engine goes through the flywheel, onto the clutch plate and into the gearbox…


The cheap way to lighten the flywheel is to turn it down on a lathe… this means it’s obviously balanced but its weakened loads as its thinner.

This is what happens when it’s turned down too much:
http://i160.photobucket.com/albums/t189/Joesnowbo/evo5.jpg
http://i160.photobucket.com/albums/t189/Joesnowbo/evo3.jpg
http://i160.photobucket.com/albums/t189/Joesnowbo/evo4.jpg
http://i160.photobucket.com/albums/t189/Joesnowbo/evo6.jpg
http://i160.photobucket.com/albums/t189/Joesnowbo/evo1.jpg
http://i160.photobucket.com/albums/t189/Joesnowbo/evo2.jpg

The expensive and more skilful way of lightening it would be to machine holes though it on the outer surface… this would reduce the inertia while keeping more strength but would require skill to make it perfectly balanced… even then the effects aren’t great apart from in neutral or maybe a bit in 1st and 2nd.

The only way forward imo is to get a different flywheel altogether along with a paddle clutch… the one below is a pugsport one and retails at 1393.94 euro's so it’s not cheap but it’s strong and you should be able to notice a difference

http://i160.photobucket.com/albums/t189/Joesnowbo/pugsportflywheel.jpg

[Toad]

Yes, it's a good point to mention about where exactly the weight is taken out from in the flywheel. Assuming the wheel is the same size, reducing weight from the outter most point will produce the most desired results. In Laymans terms, it's a bit like why sticking 17" rims on your Saxo is a bad idea for performance. Even if the 17" rims are light, having the weight further from the centre point is obviously bad.

I wish I could find this documentation I read on the Net once. It calculated the effects of a lightened flywheel in a nutshell. All you needed was the original and new flywheel weight, and the weight of the car, and it would give a rough figure to what the difference in acelleration would be. In the low gears is where the difference is seen, it doesn't make a whole lot of difference in the high gears.

So, as well as the engine being able to rev more freely, you will see performance increases too. I know it's a rough estimate, but I believe in a typical car like a Saxo, a realisticly lightened flywheel would play the role of the car losing around 100kg in weight when acellerating in 1st gear.

[spencer_cammedvts]

This What You Were Looking For Me Old Cocka?





PUMA RACE ENGINES - LIGHTENING FLYWHEELS - AN EXERCISE IN ROTATIONAL DYNAMICS
When the flywheel of a car is lightened it can have a great effect on acceleration - much more than just the weight saving as a proportion of the total vehicle weight would account for. This is because rotating components store rotational energy as well as having to be accelerated in a linear direction along with the rest of the car's mass. The faster a component rotates, the greater the amount of rotational kinetic energy that ends up being stored in it. The engine turns potential energy from fuel into kinetic energy of motion when it accelerates a vehicle. Any energy that ends up being stored in rotating components is not available to accelerate the car in a linear direction - so reducing the mass (or more properly the "moment of inertia") of these components leaves more of the engine's output to accelerate the car. It can be useful to know how much weight we would need to remove from the chassis to equate to removing a given amount of weight from the flywheel (or any other rotating component). There is more than one way of solving this equation - we can work out the torque and forces acting on the various components and hence calculate the accelerations involved - also we can solve it by considering the kinetic energy of the system. The latter approach is simpler to explain so this is the one shown below. Copyright David Baker and Puma Race Engines
Let's imagine we take two identical cars - to car A we add 1 Kg of mass to the circumference of the flywheel at radius "r" from the centre. To car B we add exactly the right amount of mass to the chassis so that both cars continue to accelerate at the same rate. If we accelerate both cars for the same amount of time they will end up at the same speed and will have absorbed the same amount of kinetic energy from the engine. In other words, the additional 1 Kg in the flywheel of car A will have stored the same amount of kinetic energy as the additional M Kg of mass in the chassis of car B. To solve the problem of the size of M we need to use the following definitions:
V - the speed of either car after the period of acceleration
R - the tyre radius
G - the total gearing (i.e. the number of engine revolutions for each tyre revolution)
r - the flywheel radius (i.e. the radius at which the extra mass has been added to car A)
M - the amount of mass added to the chassis of car B
Kinetic energy is proportional to ½mv² - the kinetic energy stored in the extra chassis mass in car B is therefore ½MV².
The extra 1 Kg of flywheel mass in car A stores linear kinetic energy in the same way as if it were just part of the chassis. After all, every part of the car is travelling at V m/s - so it stores linear kinetic energy of ½ x 1 x V² = ½V².
To find out how much rotational kinetic energy the 1 Kg stores, we need to know the speed the flywheel circumference is travelling at. The car is travelling at the same speed as the circumference of the tyre (assuming no tyre slip of course). We know that for every revolution of the tyre, the flywheel makes G revolutions. However the flywheel is a different size to the tyre - so the speed of the circumference of the flywheel is VGr/R. The rotational kinetic energy is therefore ½(VGr/R)².
Now we can put the whole equation together - the extra kinetic energy in the chassis of car B = the sum of the linear and rotational kinetic energies in the 1 Kg of flywheel mass of car A - therefore:
½MV² = ½V² + ½(VGr/R)² =>
½MV² = ½V² + ½V²(Gr/R)² => divide both sides by ½V² to arrive at the final equation:
M = 1 + (Gr/R)²
That wasn't so bad then - we managed to avoid using true rotational dynamics involving radians and moments of inertia by considering the actual speed of the flywheel circumference. This did of course involve assuming that all the mass added or removed from the flywheel was at the same radius from the centre. In the real world that is not going to be the case so we need to use moments of inertia rather than mass to solve the equation. The simple equation above is useful though in getting an idea of the relative effect of lightening components provided we have a good idea of the average radius that the metal is removed from. It can be seen that gearing is an important factor in this equation. The higher the gearing the greater the effect of reducing weight - so for a real car the effect is large in 1st gear and progressively less important in the higher gears. We can also hopefully see that when r is larger, so is the effective chassis weight M. So removing mass from the outside of the flywheel is more effective than removing it from nearer the centre. Copyright David Baker and Puma Race Engines
It might at first look as though tyre diameter is important but of course it isn't for a real car - if tyre size was to change then so would gearing have to if overall mph per thousand rpm were to stay the same - the two factors would then cancel out again.
To show the sort of numbers that a real car might have, I did some calculations based on a car with average gear ratios and tyre sizes - the table below shows the number of Kg of mass that would have to be removed from the chassis to equate to 1 Kg removed from the O/D of the flywheel at a radius of 5 inches.

GEAR MASS KG
1 39
2 12
3 6
4 4
5 3
So in first and second gear this is a pretty important effect - I built an engine recently and managed to remove nearly 3 Kg from the outside of the standard flywheel - so that would be equivalent to lightening the car by over 100 Kg in 1st gear - not to be sneezed at in terms of acceleration from rest. With special steel or aluminium flywheels even more "moment of inertia" can be saved. The recent trend in racing engines to using very small and light paddle clutches and flywheels is therefore more effective in terms of the overall performance of the vehicle than it might first appear. Copyright David Baker and Puma Race Engines
There's a final consequence of the "flywheel effect" being dependent on gearing. Small highly tuned, high revving engines need to run much higher (numerically) gearing than large, low tuned engines. This means that the effect can be very pronounced on them. Bike engines are a good case in point, especially as they are now starting to be used in cars so much. A 100 bhp bike engine might only be 600cc and rev to 12,000 rpm. A 100 bhp car engine might be 2 litres and rev to 5,500 rpm. Put the bike engine in a car and you'll need to run a final drive ratio twice as high as for the car engine. As the flywheel effect is proportional to the square of gearing, it will be 4 times as high for the bike engine. You could therefore be talking about 1kg off the flywheel being equivalent to 160kg off the weight of the car. That's why bike engines have such small multiplate clutches to keep the moment of inertia down. On the other side of the coin, it's not worth spending much money lightening the flywheel of a 7 litre Chevy engine revving to under 5,000 and geared for 60 mph in first as the vehicle will be very insensitive to the reduction in weight. Copyright David Baker and Puma Race Engines
If you are going to get your standard cast iron road car flywheel lightened then be sure to take it to a proper vehicle engineer and not just your local machine shop. Take off too much material and it might be weakened so much that it explodes in use. Given that flywheels (at least in rear wheel drive cars) tend to be situated about level with your feet, it isn't worth the extra acceleration if you lose both feet when the ring gear comes out through the side of the transmission tunnel like a buzz saw at 7,000 rpm. There are plenty of ex racing drivers hobbling about on crutches who'll tell you that this can and does happen. On FWD cars the effects can even more unpleasant - a flywheel entering the cabin can give you a split personality starting from just below the waist that will put quite a crimp in your day. Also when you remove any weight from the flywheel it will need re-balancing again properly. We'll be happy to do the job for you if you don't know of an experienced engineering shop.
Addenda (May 2002). A friend, Garry, told me an interesting story the other day which relates to my warning above about lightening flywheels properly. He was at the local engine reconditioners chatting to the proprietor about having a cylinder head skimmed. At the back of the workshop, one of the lads who worked there was lightening a flywheel on the lathe. Suddenly there was an almighty bang and a lot of swearing so Garry and the owner went back to see what had happened. The lad had been removing material from the centre of the flywheel, just outboard of where the 6 crankshaft bolt holes are. For starters this is a stupid place to remove material because it is a highly stressed area and also much less effective in terms of the reduction in inertia than removing material from the rim of the flywheel. Anyway, to cut a long story short this idiot had machined right through the flywheel leaving the centre attached to the chuck of the lathe and the rest had flown off and bounced across the workshop. It made me wonder what would have happened if he'd stopped just short of machining right through, say with only 1mm thickness of material left, without realising how thin and weak he'd made it. It would then have failed in the car, maybe at high rpm, and done the sort of damage I describe above. The moral is clear. Get critical work like this done by someone who knows what they are doing.
An average cost to lighten and rebalance a cast iron flywheel it £80 but best to email and ask about your specific application first.
Copyright David Baker and Puma Race Engines
Other Rotating Components
All other components which rotate absorb energy in addition to them having to be accelerated linearly along with the chassis. Components which rotate at engine speed like flywheels are the most cost effective ones to lighten in terms of their equivalent chassis mass but it pays not to overlook the mass of any rotating component. The next major category is items which rotate at wheel speed - wheels, tyres, discs etc. These don't rotate as fast as engine components but they can be very heavy. The average car wheel and tyre weigh about 45 lbs together. A good rule of thumb is that in addition to its own normal weight a wheel speed item adds the equivalent of an extra 3/4 of its mass to the effective chassis mass and this figure is not dependent on gearing so it stays a constant at all times. It's a smaller effect than the flywheel effect which can be many times its own mass in first gear but still important. Let's say you fit wide wheels and tyres to your car. If each corner weighs an extra 10 lbs more than the standard items then the effective increase in chassis mass is 40 lbs for the direct weight plus another 30 lbs being 3/4 of the direct mass - a total of 70 lbs. On a light car like a Westfield or hillclimb single seater this could be between 5% and 7% of the effective total car weight. Equivalent to knocking the same percentage off the engine's power in acceleration terms. That's why F1 and other high tech series designers strive so hard to reduce weight in this area and use magnesium instead of aluminium for wheels and the thinnest possible carcasses for tyres. It also reduces unsprung weight of course which helps the suspension and handling. Even on a 1 ton road car the effect of heavy wheels and tyres can be noticeable in terms of reduced acceleration. Wider tyres also absorb a bit more power in friction which doesn't help either if the engine is on the small side. Copyright David Baker and Puma Race Engines
The other few rotating items, gearbox internals, camshafts etc are generally of small diameter and not worth lightening because of their consequent low inertia. One thing I can promise you is that the current fad for anodised aluminium cam pulleys which then usually get hidden behind a cover anyway won't make a scrap of difference to your engine because of the few grams weight they save. They may well wear out and cost you your entire engine if the teeth strip off the belt though. Aluminium is not really the material for gears and sprockets but when did fashion and common sense ever go together?
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This article is the intellectual property and copyright of David Baker and Puma Race Engines. Reproduction in whole or in part without written permission is strictly prohibited.

[Toad]

It might be!!! Although I haven't got a spare week to read that just now. ;) I'll certainly take a butchers soon though. Good lad.

[Gabbastard]

This What You Were Looking For Me Old Cocka?






This article is the intellectual property and copyright of David Baker and Puma Race Engines. Reproduction in whole or in part without written permission is strictly prohibited.


LOL oops

[Joesnow]

I’ve read all that before and was going to say that it’s all copyrighted lol! Probably best to edit that post lol! That guy is a legend and has some class articles… well worth a read of his site…

Those figures are calculated from 1kg that’s been taken from a radius of 5”… I’m sure a while ago when I had a look into it and nothing like 1kg could be taken off and that wasn’t at a radius of 5 inches so the effects won’t be that great…

[Euphoria]

I was thinking about getting a type r, but after seeing that vid of the vts it makes me wonder whether i should just get a vts and cam it, rather than grab myself a type r :S whats the drive like? has it got the fun factor like Vtec? with the extra power, how does the drive shafts and other components handle? Obviously making a vts that can do 0-60 in 6.5secs will defo need an upgrade on the brakes! Lol

[Karl]

Cheaper and slightly quicker to 60 than a Type R,

obv Type R is a better car,
but the Saxo will be alot cheaper and imo a more fun car to drive.

[Ry_B]

Saxo will surprise more

[Euphoria]

Saxo will surprise more

LOL yea i guess it would :D

[pug205gti87]

nothing worse than having a £12000 type r and gettin panned by a saxo :P

[spencer_cammedvts]

12000 lol and the rest. more like 18-19k

[williamsvts]

get a nova :P

[spencer_cammedvts]

old cars are the best man cause you dont expect them to be fast. soo much more satisfying when you smoke bigger more expensive cars :)

[Toad]

I will advise on a standalone ECU. I've had 708s running with a chipwizards' map for a while now, and I'm convinced the car performes differently time to time. It's seemed a little flat the past week or 2, but it will pick up again... So wierd.