Decompression plate questions....

[Tannerman]

Sorry guys I'm beasting you with questions tonight

1) how much power can I run before having a decompression plate just isn't enough?(need new pistons/rods)

2) does anybody no a reliable place to buy them from as iv searched for them and they range from £50 - 260 euros n I can't see how the price can vary that much unless the quality of the plate is stupidly different.

Any other insight to this would be great...cheers

[NismoSteve]

I'm interested in the answers to these questions too.

[stevo1600]

Ferriday engineering. It's where I'm getting my decomp plate from. I'm going for a 1.9mm. You also have to bond it to the block with the paste they sell. I've heard nothing but awesome quality comments from peeps on here who have had a decomp from them. think it's close to 130 quid iirc.

Standard pistons are good but they hate heat. This is why we fit forge pistons as they can cope with more heat and other stresses etc.

Decomp ain't gunna pop easily mate, so you can run over 200 bhp on decomp.

[NismoSteve]

sounds reasonable, what kind of power are standard pistons happy to run at, I'm guessing quite low boost on a T25?

[Tannerman]

My target power is no more than 225 so would standard pistons be ok with that or would I be pushing my luck?

Was looking at ferriday just they didn't have no prices up cheers mate

[blackie_2k5]

Decomp is bonded to the head not the block, it's meant to work as an extension of the head, old beliefs are decomps don't work and any more then 8psi boost is unsafe, but these beliefs all stem from practise on old engines, what we're seeing more now is that the Saxo engine set up properly can handle a fair bit more reasonably, you have to realise the more you run the more unreliable it'll be. With 8psi and good maintenance I see no reason it won't last as long as a normal engine, I'm running 15psi for 6k of abuse now, lots have others have done similar, wouldn't really wanna go higher, although I soon will be as I opted to run very low compression

[Tannerman]

Ok cheers for that mate.got quit a few parts already but money's hit a dead end now so gotta wait till after Xmas.lol.Need to find else what I need aswell.lol

[NismoSteve]

Good info, what's the preferred management run run a low boost setup on standard internals?

[rorz_vts]

the ferriday decomps are really nice bit of kit well worth the £135 price tag with the paste,

steve they only come in a 1mm or 2mm just to let you know think you mixing sizes up with the HG's

[dannygti]

If using a Decomp plate and higher boost I recommend getting head studs.

[NismoSteve]

Cheers, arp for the stud kit?

[stevo1600]

Thanks blackie, I knew I'd gotten that part wrong.

Yea I'm thinking hg lol. Going for the 2mm.

Danny what you mean head studs? You talking about the two little collars that keep the head lined up on the block? I had trouble when fitting my double hg as they were to short.

[Gandi699]

Thanks blackie, I knew I'd gotten that part wrong.

Yea I'm thinking hg lol. Going for the 2mm.

Danny what you mean head studs? You talking about the two little collars that keep the head lined up on the block? I had trouble when fitting my double hg as they were to short.

I assume he means a kit of long studs and nuts instead of head bolts so you get a more accurate torque rating when doing them up. Plus they are re-usable I believe

[toger13]

have you seen the price of head studs? lol

get some forgies in there lol

Si

[dannygti]

have you seen the price of head studs? lol

get some forgies in there lol

Si

£150.. They are a worthwhile investment when using Decomp plate. The extra clamping force is needed when there is another surface to leak from.

[NismoSteve]

I've used stud kits before in my jap builds along with rod bolts too.
My last SR20 build I sent the crank, rods, and pistons off for cryogenic freezing. Check out www.frozensolid.co.uk gives peace of mind to high output engines.

[Tannerman]

Cheers for the help guys.starting to see a light at the end of the tunnel.lol

[toger13]

ye i use Studs and nuts on mine but on a budget build the money would be best spent elsewhere plus they need to be retorqued every so often not good unless you have jp4 rockers :-)

150 for studs and nuts
150 for decomp plate

how much are forgies nowadays 400?

Si

[NismoSteve]

True, but if you go forged you may as well rebuild the bottom end so There's more expense.

[Tannerman]

Plus you can pic up decomp plates alot cheaper n I think your looking at closer to £700 for some forgies surly?

[NismoSteve]

That's a ridiculous ammount for forged pistons, I used to get Wiseco forged pistons for the Nissans at £375 a set and they were really good quality.

[dannygti]

ye i use Studs and nuts on mine but on a budget build the money would be best spent elsewhere plus they need to be retorqued every so often not good unless you have jp4 rockers :-)

150 for studs and nuts
150 for decomp plate

how much are forgies nowadays 400?

Si

I don't agree si, think anyone who wants to run around 1bar+ on a Decomp plate a set of head studs is a good idea. Proper clamping force across the head. There's a lot less residual load in the head with normal bolts.

Pistons are around 500+vat as a rule at the minute.

I agree pistons are by far the vest way but it's not just 500+vat is it... It's the. Rebore and hone etc and having to take your engine out for it.

[Tannerman]

Ah I was assuming u meant rods aswell

[NismoSteve]

Yeah pistons and rods are £849 somewhere I've seen? Plus rebore, gaskets, seals, mains and big ends. A dear do then. And if your going that far There's balancing and a top end rebuild while its apart, lifters and cams lol! Full on rebuild.

[Tannerman]

Yeah pistons and rods are £849 somewhere I've seen? Plus rebore, gaskets, seals, mains and big ends. A dear do then. And if your going that far There's balancing and a top end rebuild while its apart, lifters and cams lol! Full on rebuild.

I ain't that keen....prefer to just keep it at a manageable power.lol

[NismoSteve]

decomp plate it is then:)

[Tannerman]

Lol.yeeeeeep

[rorz_vts]

I'd go for a decomp first see how you find the power etc then if you want more later buy a spare bottom end and get all the work done whilst you still enjoy your current build.

Thats what I'm doing anyway :y:

[NismoSteve]

I'd go for a decomp first see how you find the power etc then if you want more later buy a spare bottom end and get all the work done whilst you still enjoy your current build.

Thats what I'm doing anyway :y:

+1 that's the way I'm gonna do it too.

[e8_pqck]

Thanks blackie, I knew I'd gotten that part wrong.

Yea I'm thinking hg lol. Going for the 2mm.

Danny what you mean head studs? You talking about the two little collars that keep the head lined up on the block? I had trouble when fitting my double hg as they were to short.

2mm HG + 1.9mm decomp will lower compression to much i think and run like a dog off boost. Really no need to go that low.

[dannygti]

2mm HG + 1.9mm decomp will lower compression to much i think and run like a dog off boost. Really no need to go that low.

I agree, 2mm Decomp plate and 1.2 gasket would be better imo

[Tannerman]

Fuckin hell why can't it just be easy.lol

[blackie_2k5]

I agree, 2mm Decomp plate and 1.2 gasket would be better imo

thats about optimum, thats about what we worked off but i went for 1.4ish

ppl that read my thread must understand the head i had was on bare bones and was only ever going to be a tester as a foot bridge to more, it was already on its limit and i had a light shave done as i knew there was a decomp going on

i have 1.9mm gasket and 2mm decomp, car runs awesome on/off boost, and is lasting alot longer then i thought..

edit- im happy to run a bit more boost at the cost of CR as i dont IDEALLY want it to burst..

[blackie_2k5]

Fuckin hell why can't it just be easy.lol

if it was easy...everyone would be doing it :p

[dannygti]

thats about optimum, thats about what we worked off but i went for 1.4ish

ppl that read my thread must understand the head i had was on bare bones and was only ever going to be a tester as a foot bridge to more, it was already on its limit and i had a light shave done as i knew there was a decomp going on

i have 1.9mm gasket and 2mm decomp, car runs awesome on/off boost, and is lasting alot longer then i thought..

edit- im happy to run a bit more boost at the cost of CR as i dont IDEALLY want it to burst..



I'd much rather have higher compression and less boost which is what I am doing.

[Tannerman]

if it was easy...everyone would be doing it :p

True...just wish I was a guru then it would be easy.why can't it just be , TURBO-BOLT ON-GO.lol

[saxova]

True...just wish I was a guru then it would be easy.why can't it just be , TURBO-BOLT ON-GO.lol

You can just bolt it on and go.

Just how long it will last is the problem :P

The key to any turbo build is management and a good map.

[Tannerman]

I no mate I was kidding.lol.

[toger13]

you could always just get comtic to make you a custom gasket i use a 2.3mm one on mine

Si

[blackie_2k5]

I'd much rather have higher compression and less boost which is what I am doing.

what is the CR your running danny, i wouldnt say mine was massivley low, drives fine on and off boost so its all worked out well :)

[tweeqd]

my 1st engine had 1mm low comp pistons, a 2mm decomp plate and a 1.4mm gasket
couldnt really drive it off boost as it was on full boost by 2k but would of made alot more power with a higher CR

the only reason i have kept my new one under 9:1 is i am running nitrous aswell as boost

ill be useing the decomp plate as the HG with the 16v head

[dannygti]

what is the CR your running danny, i wouldnt say mine was massivley low, drives fine on and off boost so its all worked out well :)

Runs well yes, but could it be/feel better? The only way you can find out is if you do and then you will know the difference.

My compression ratio is 9.3-1 but I want to make it 9.5-1 with my new bottom end.

[blackie_2k5]

im sure with a slightly higher CR it "could" feel/go a little better, but is that at risk of how long itll last...

it goes well enough and made fair power so im happy for now, need forged pistons and rods :D

[NismoSteve]

im sure with a slightly higher CR it "could" feel/go a little better, but is that at risk of how long itll last...

it goes well enough and made fair power so im happy for now, need forged pistons and rods :D

Your car is a real inspiration mate. Its one of the cars that's convincing me to sell the turbo xsara when I've finished it and get some boost into the saxo. Trouble is I don't know whether to stick with the 8 valve or go 16.

[blackie_2k5]

thanks mate its nice to hear :), i like to think it has helped a few ppl tbh... i never had the biggest budget but that never stopped me,

so if nothing else its nice to think it may have shown some ppl that money isnt alway the be all and end all :y:

and its made good power :D

EDIT- also, if it were me allover again, id be a sheep and go 16v, just becuase i want more now :D but mak no mistakes mate, the 8v its seriously quick atm, and youd really be surprised what cars it puts to shame... i love the fact its 8v which is why i want to stay with it and forge it, no greater feeling then telling ppl its a 1.6 8v :)

[NismoSteve]

Exactly, I was really impressed with your dyno results and your spec. I've got a vtr lump, loom and ecu that I'm thinking about dropping in the desire and taking to a similar spec to yours.

[blackie_2k5]

go for it mate, it WILL make you happy lol,

dyno results should always be taken with a pinch of salt tbh, as most are quite unrealistic unfortunatley, and ppl will always question them

the dyno i used is known to be accurate...

but still had i not seen about 60-70 cars over then 2 different dyno days, all with varying driven wheels and specs, id have probs questioned mine tbf, but all the figure matched the specs and expected outputs.... there were about 5 cars with problems the dyno highlighted (including mine in the first day) which didnt make expected, but you could even tell by smells and smokes of these cars they had issues

also had a couple the were dyno'd at another dyno's, days or weeks before that were only a few bhp diff then on the days, so im pretty confident theyre fair...if anything the dyno reads sligthly under in some cases

[dannygti]

What did yours make atw blackie?

[NismoSteve]

What did yours make atw blackie?

I've started reading through your progress thread today Danny, its going to take me a bloody week to get through that!

[blackie_2k5]

Think it was around 185atws Danny, I'll dig the graph out later, packs a punch though lol

[dannygti]

Think it was around 185atws Danny, I'll dig the graph out later, packs a punch though lol

You don't need to tell me that lol I know how fast they are haha

I've only used 10% transmission losses :|
it's interesting to see different places use different losses.

[blackie_2k5]

Yeah, mine was about the same as adz's supercharged S at the wheels but his made about 2bhp more ATF,


What were you fly figures?

[dannygti]

10% on 250 so 275@flywheel. If I used your lads % it would give me around 290@flywheel

[blackie_2k5]

Yeah I think mines somewhere in the region of 15%, I've not worked it out tbh, I might do later if I get time, does anyone know the correct transmission loss on the Saxo set up is?

The dunno I use belongs to an Evo specialist, so may be set up for tranny loss on those, but may also be set up as a general loss, as most run off about 10-20% don't they

[dannygti]

Yours works out to 18%. my car would be 297@flywheel using that figure lol
There's no set % for losses. The only way to get true engine power is engine dyno. Flywheel power Is a guess really and it depends on who's rollers you use TI what losses they will give you. Lots of things can effect power at flywheel so that's why you should take those figures and forget them.

[blackie_2k5]

yeah i know mate, i just thought the likes of sandy may know a good estimate for tranny loss through the saxo/106 set up, being as he does alot of engine dyno work

pity as it'd be handy to have tbh...i know itll never always be the same, but a good figure to work off may help

im just happy with how it goes tbh, i never really had the intention of making big figures, i just wanted it to make about 200bhp for A.. having that magic number.. and B from reading up it what most ppl deemed a very quick car for a saxo/106

so even on 10% losses ive tipped it :) which is pretty cool tbh

[dannygti]

Definately good going mate, I'm not trying to knock anyone's work or cars for that matter I just find it wierd how there can be such a large difference in losses.

When my car was making 180'ish atw it was rapid and no normal stuff on the road can keep up.

[blackie_2k5]

oh i know, mate, its all about the percentages though really, the more you go the bigger the diff is..

thats why alot of supposedly high figure'd car's get shown up by cars that were allegedly running alot less. and why ppl should only take numbers with a pinch of salt :D

dyno is better as a health check then anything else

[Sandy309]

The only thing you need to know about rolling roads, is that the figures are estimated. Transmission loss is a real misnomer, the tyres account for a large proportion of the loss. The actual gearbox and final drive loss, with a healthy box, is about 8-10% of flywheel power (going by the engines we've run on hub dynos after the engine dyno); the rest is the tyres and that can vary hugely (twin rollers have much greater tyre loss than single rollers), that's the simplest way of looking at it.

To look deeper, you need to consider how the wheels figures are obtained. Traditionally (older analogue rolling roads), the rollers are braked by a large eddy current retarder, which leans on a load cell. The load cell reading is literally torque; to make matters worse, the torque is mulitplied by gearing and tyre size. Older rolling roads simply work on an average gearing to convert to torque at the wheels and typical rpm to get power at the wheels; all of that averaging and multiplication means that "wheels power" is not a literal figure, it's calculated as an estimate and accuracy varies with gearing and tyre size, significantly! The coast down after was dreamt up to try and estimate the transmission loss; but older systems basically measure the free running inertia, not the actual power absorbtion of the transmission (that's a major point) and of course the situation under full power is quite different.
Over the years, computers and improving software allowed the rollin road manufacturers to get better as estimating, taking more factors into account and more data to improve the averaging of the losses etc. But the principals are still the same, you have a load cell on the brake and try to correct it by better calcuation of the gearing reduction, then estimate the transmission/tyre losses. If you're doing the same cars all the time, in similar condition, you can achieve good repeatability, but beyond that, there are still several ways that the figures can be corrupted.
Different rolling road systems calculate the wheels and loss figures in different ways, so you can't compare very well between systems. For example, MAHA LPS3000s, generate relatively low wheels figures and high losses, that don't compare with the lower loss and higher wheels figures from Superflow and TAT are somewhere in between, also twin rollers work differently to single rollers.

All systems struggle to cope with the way tyres behave at different speeds and generally, if you run a car at very high roller speed (ie over 120mph), the system will usually over correct the tyre losses and the figures get inflated; conversely at low roller speed (under 80 mph), tyre losses get under compensated usually. Tyre distortion reduces at high speeds as the carcass expands through rotational inertia and recedes the contact patch, but the rolling road will continue to slope the tyre drag upwards, according to the pattern of the lower part of the curve. How the car is strapped can also affect that scenario.
If you want to get precise figures, a properly calibrated and corrected engine dyno, is the only way.

[rorz_vts]

cheers sandy that was a great read, opened my eyes to RR's and used and how the powers worked out.

[e8_pqck]

it all sounds very academic.

fact is we all use wheel dyno's, they all vary slightly and they are roughly the only way of measuring our power outputs.

So if mine makes 500 and blackie's makes, say 5 for instance, i'll say mine is 495bhp more powerful.

[stevo1600]

True, it's the only way of getting a bhp figure.

But To be honest RR figures don't mean 'that' much to me and should always be taken with a pinch of salt.

I'm not that bothered what figures I end up making really, I'm way more interested in how it feels to drive, how power Is planted etc. yea it's nice to know what you have built and the power it's achieved but I bet your not thinking about it when your pinned in the seat changing gear every few seconds.;) so personally id concentrate on that rather than chasing figures. it would be nice to achieve a bang on figure, but as sandy explained thats not Exactly possible with all the different conditions etc.

Awesome info m8 :clapping:

[axsaxoman]

If you really want the best figures ,then pay some more and go to someone with a hub dyno and just use the figures it measures as they will be power you are showing the road and because it is bolted to yuor hubs there is no tyre slip facotr of any type .
one word of caution i know of a couple of cars that had lots of wheelspin on std type dyno,s and wnet to a huib dyno --
and proceeded to snap a driveshaft and in one case and destroyed the clutch in the other .
the wheelspin can act as a good powr dampener --there is no slip with a hub dyno

when all said and done the flywheel figure is for the "pub"
its only power @wheelsthat makes it go forward

[blackie_2k5]

I feel when I get some better tyres up front I'm gonna lose a shaft tbh, I can feel their pain atm and thats with lots of wheelspin :(

[axsaxoman]

I feel when I get some better tyres up front I'm gonna lose a shaft tbh, I can feel their pain atm and thats with lots of wheelspin :(

and thats where we come back to my preference for the s/c--controlability
I am awaiting someone wanting to using a proper modern vnt turbo with a proper ecu to control it all -then it could be different -as of course the costs would be

[luthor1]

Blackie - we need to get you setup properly with, say, a 4-5psi actuator and a solenoid conrtolling the rest of the boost pressure, mapped against throttle position and RPM on a 3d MAP.

That'll sort you out

[NismoSteve]

I had racelogic traction control on the supra and S14, that's good kit and you could use that to save shafts and box.

[blackie_2k5]

i think my new wastegate has a 6 or 8psi spring in it...that should be fine as a starter tbh, have you looked into any solenoids youd like to use?

we'll have to talk more about the fitting and move from there :y:

[axsaxoman]

that will depend on what rpm you need to obtain the 6-8psi--if its a "laggy turbo then you will still get the sudden increase in power--control is only part of it ,the turbo must be capable of spooling up in an orderly manner ,then you control how it comes on --as andy is suggesting .
evo 6 /7/8( not evo4/5)is a typical good unit as you can get around 12psi+at 2200rpm (on a 2litre engine)--so it it will probably be 3k+ for a 1600-- now control that correctly and you are getting closer--lift the comp ratio and control it better is the answer,add fro wheel speed sensors for traction control --spend a shit losd of time setting it up .
yes i know it isn,t the same flange as a t2 or gt28 -