Turbo set up

[Milney8989]

I'm thinking of starting a turbo set up late next year. I will be doing forged rods and Pistons so I know that the bottom end will be fine. Will use a ported and polished head as I have one just sitting here doing nothing! Have standard or743 cat cams but don't know if they will be good enough! I don't want to go for massive power as want to keep reliability! What would be a good bhp to aim for to keep reliability and also keep the driving fun?

[sri_130]

I personally wouldn't do any of that unless you're happy to spend the money, of course.

7-9psi, relatively low boost can be attained on stock internals, ecu (mapped of course), cams etc etc - potentially with a slight lowering of compression. Approximately 170ish bhp with an easily sourced GT17 as per the cituning kit of old.

Low boost on stock internals seems to be relatively reliable if done correctly. Lots of fun. It can also make the local McDonalds crew go wild when you jettison your inlet manifold pressure on a driveby.

[Milney8989]

Originally Posted by sri_130

I personally wouldn't do any of that unless you're happy to spend the money, of course.

7-9psi, relatively low boost can be attained on stock internals, ecu (mapped of course), cams etc etc - potentially with a slight lowering of compression. Approximately 170ish bhp with an easily sourced GT17 as per the cituning kit of old.

Low boost on stock internals seems to be relatively reliable if done correctly. Lots of fun. It can also make the local McDonalds crew go wild when you jettison your inlet manifold pressure on a driveby.

Well I save a lot of money doing all the bits myself with the help of my dad him being the mechanic I no my way around a car well through the years of watching and trying. Lol. I would like to do the forged bottom end just for piece of mind knowing it will be strong. Is the gt17 exactly what I need? as a lot run gt25 I believe! My mate works for a turbo recon specialist and said once I know what turbo I want he will sort 1 out for a drink so I know that will be cheap. I could do the whole build for under 2000 with all bits and bobs and I already have an omex for my throttlebodies I will be running this year. Thanks for your reply fella.

[sri_130]

Originally Posted by Milney8989

Well I save a lot of money doing all the bits myself with the help of my dad him being the mechanic I no my way around a car well through the years of watching and trying. Lol. I would like to do the forged bottom end just for piece of mind knowing it will be strong. Is the gt17 exactly what I need? as a lot run gt25 I believe! My mate works for a turbo recon specialist and said once I know what turbo I want he will sort 1 out for a drink so I know that will be cheap. I could do the whole build for under 2000 with all bits and bobs and I already have an omex for my throttlebodies I will be running this year. Thanks for your reply fella.

Forged bottom end is near enough a thousand pounds. Whilst its not my place to tell you how to spend your money, you can by 10 engines for that price... Obviously, whats right for you, is right for you.

I don't believe there is an exact recipe, most have used the GT25 and GT28 (by no means an adopted standard) when looking circa 200bhp+.
The GT17 comes in low and is easy to source for 180hp and maybe a bit more, so ideal for a low boost application. Also think about your clutch - low boost, can allow the use of the stock (but new) clutch. Reaching higher up the scale of bhp, will mean you may need to consider an upgraded item.

It tends to be 'everything else' that pile on top to increase the costs. Injectors, fuel pump, manifold, fittings and fixtures as they are not the flashy parts of the build that people immediately think of. But, I can vouch for low boost though, its great fun.
250+ horsepower in a saxo/106 is also crazy fun. I've never laughed so much in my mates. I think he has a permanent smile attached whenever he takes it out as well.

[axsaxoman]

std cams is all you need for a sensible turbo build and no need for t/bodies at all at any boost level --you wil find its a lot easier to get it running well across whole rpm range with std cams =single t/b
yes fitting pistons +rods is a good idea --for when you get the bug and wan to lift the boost more
do not assume piston ring gaps are correct !!

[Rossp]

John's summed it up well to be honest. Forge if you think you'll want more power, don't if you're keeping it under 200hp. Standard internals will be fine. 200hp is achievable on standard engine and gt17 turbo with two head gaskets. 170-180 doesn't even need the slightly lower compression of two gaskets imo.

Use standard cams for up to 300hp. Above that look at turbo spec cams. So basically don't worry about it.

Once over 160ish hp you'll be wanting to think about clutch and gearbox. If you're going above 200hp then consider a diff (John does the quaifes for a good price).

200hp is a great level to aim for - fast as fook, reliable, cheap, and fun.

[doctoromeo]

lol ross,
"170-180 doesn't even need the slightly lower compression of two gaskets imo.
"on a base of 10.8:1 base comp I wouldn't expect that to last very long though.
I think ring lands might be the first to go.

[Rossp]

Depends on your definition of "not very long"

[axsaxoman]

depends how well you set up the ecu in fuel +ign timings -but not at 1 bar --78psi yes
lower comp don,t alter the top ring thickness which is the usual dif in turbo /non turbo pistons
std turbo cars use 10:1 with 1bar of boost --so should be no prob if set -up correctly and cooling system good

[CbVtR]

Originally Posted by Ross

John's summed it up well to be honest. Forge if you think you'll want more power, don't if you're keeping it under 200hp. Standard internals will be fine. 200hp is achievable on standard engine and gt17 turbo with two head gaskets. 170-180 doesn't even need the slightly lower compression of two gaskets imo.

Use standard cams for up to 300hp. Above that look at turbo spec cams. So basically don't worry about it.

Once over 160ish hp you'll be wanting to think about clutch and gearbox. If you're going above 200hp then consider a diff (John does the quaifes for a good price).

200hp is a great level to aim for - fast as fook, reliable, cheap, and fun.

Hi-jacking this thread a little, I'm aiming for 200 ish, I already have a 6 paddle clutch and clutch cover, but you have got me worried about the gearbox now lol.

I know its a bit like how long is a piece of string, but any idea how long a standard box would last at 180-200 hp.

Is the BE the only option as I always thought the diff was the weakest link in the MA box?

[iSlayeR]

Originally Posted by CbVtR

Hi-jacking this thread a little, I'm aiming for 200 ish, I already have a 6 paddle clutch and clutch cover, but you have got me worried about the gearbox now lol.

I know its a bit like how long is a piece of string, but any idea how long a standard box would last at 180-200 hp.

Is the BE the only option as I always thought the diff was the weakest link in the MA box?

My first vtr gearbox lasted about a month, my vts gearbox is still coping after about 3 months (touch wood) mines a 160hp turbo vtr but ye standard boxes are pretty crap lol

[Rossp]

Originally Posted by CbVtR

Hi-jacking this thread a little, I'm aiming for 200 ish, I already have a 6 paddle clutch and clutch cover, but you have got me worried about the gearbox now lol.

I know its a bit like how long is a piece of string, but any idea how long a standard box would last at 180-200 hp.

Is the BE the only option as I always thought the diff was the weakest link in the MA box?

We found the "weakest link" is the MA casing not the diff. When given a lot of right foot, lots of torque, the gearbox casing flexes and actually pulls the layshaft and the mainshaft apart enough that the gear teeth don't engage fully in each other, and you can strip gears.

The other danger of higher power (from the gearboxes perspective) is smashing the diff - if you drive over ground where one wheel has less traction than the other (say, a back road with bumps) when one wheel starts to lose traction then regain traction, it causes considerable stress to the diff. An aftermarket diff solves this problem as it's stronger, but (in my opinion) is only moving the problem somewhere else.

If I were building a cheap car, for 170-180hp, I'd stick with standard boxes and just treat them as consumables. When they break they break. If I were building something that needed some reliability or with more than 200hp, I'd want a BE box in there as the casing is much stronger and the diffs are so easily changed.

All my opinion of course - take it or leave it

[axsaxoman]

must be at least 30+s/c cars running eith ma with no problems
usual thing is when people say they have fitted a "NEW" box --they mean a s/h one of unknown quailiyt
if your ma is rebuilt and used sensibly it wil take 200 no problem -
when you remove g/box oil drain if oil is grey then it is worn -thsoe grey bits are dif casing swarf-strip every gear off shafts clean out all crap +rebuild totally with new bearings any s/h box you get and it will be fine -unless you want to wheelspin it all the tinme --then fit lsd

[Rossp]

Originally Posted by axsaxoman

must be at least 30+s/c cars running eith ma with no problems
usual thing is when people say they have fitted a "NEW" box --they mean a s/h one of unknown quailiyt
if your ma is rebuilt and used sensibly it wil take 200 no problem -
when you remove g/box oil drain if oil is grey then it is worn -thsoe grey bits are dif casing swarf-strip every gear off shafts clean out all crap +rebuild totally with new bearings any s/h box you get and it will be fine -unless you want to wheelspin it all the tinme --then fit lsd

Key here being SC - which as we know doesn't put its torque down anywhere near as aggressively as turbo. If you fit an lsd into an MA box with turbo, you'll simply transfer the stress into the casing IMO, causing even earlier failure.

Turbo + MA = short life expectancy - in my opinion.

To the OP - Of course, it's not my car being built so... you do what you think best. People will always have different opinions

[Gandi699]

MG-rover used a development of the MA box in their small to medium cars in the 90s-2000s as did the early 1.6 naturally aspirated Tritec BMW Mini. Various upgrades and changes were made from the standard MA box by both companies, different selector forks to contact the synchro hubs, changes to how the diff is attached and various other things.
Even with this work done these boxes were never put in any of the larger engined/performance car (1.8 K-series/Cooper S) which were developing significantly less power and torque than a turbo charged TU would be putting out, even one in a mild specification.
They were then dropped and replaced with honda, ford and getrag units respectively across the various ranges even in the low spec cars.
Guess that probably gives you some indication of the MA boxes strength and the problems encountered with it.
That said I ran 143bhp/128+lb/ft metro on an R65u (ie: an upgraded MA) and didnt have a problem but it was driven reasonably sympathetically which I think is crucial.

[stevo1600]

Im glad this thread has popped up.

Im almost done with my list parts for my turbo conversion on a 106 gti - im aiming for around 230 bhp.

I have a couple of questions for the turbo gurus, Firstly compression.

As you have mentioned ross, 2 x headgaskets clamped together should be fine for 200bhp? what about 220-240? can i get away with that compression method? also what size gaskets? gmc do different thicknesses.

I have "heard/read" one 1.9mm mls headgasket should be ok but would like to confirm this first.

The core parts of my build are as follows, let me know what you guys think.

Fueling.

Predator ecu
Meganne 225 injectors
4bar fpr????? do i need this or will standard fuel pressure be ok?
walbro fuel pump

The bits.
Gt25turbo from a saab 9-3 2.0t
equal length adapted 200sx s13 manifold
2.5inch exhaust
c2 inlet
normal sized intercooler - 2inch pipes.
helix paddle clutch
ma box
double headgasket method

Yes i know theres load more parts these are just the core parts.

would 200 be achievable? id really like to see that magic 220-230 though.

[Rossp]

There's cars out there doing 200hp on standard compression - the key really is in the mapping. With a standalone like the predator, and adding two gaskets or even the 1.9mm gasket *should* be just fine. The lowering of compression is to try to stop knock, and knock is caused by temperatures and poor fuel/mapping. So using 99 ron fuel, on a well setup map (critical) and keeping the temps low (good intercooling / turbo in efficiency island) will all play a vital part in your setup.

I don't know enough about the higher-comp / lower boost builds to speak with real authority so I don't want to say something for you to go and do it, only to be proven wrong (at your expense). so take what I say with a grain of salt and speak to others more knowledgable than I. John at GMC is a great example. If you're going to order head gaskets order them from him - he'll also give you some advice on what's achievable (even if he will tell you how much he dislikes turbos vs superchargers!).

Spec wise...

I thought the saab 9-3 turbos were t25's not gt25's?
2" pipework for intercooler is ideal. Don't look as bling as 2.5" under the bonnet, but much easier to route and keeps lag to a minimum.
Think about a diff at >200hp. You're going to get a lot of wheelspin. John can look after you here with a quaife for the MA if needed.

Regarding your injectors, this should help: http://www.saxperience.com/forum/sho...d.php?t=427727

[stevo1600]

Thanks for that ross - appreciated.

Regarding turbo, your most likely correct, i will have to look into this a bit more.

A key part of my build is going to be keeping temperatures down so i can reduce the chance of it causing damage to the engine, i know the tu engine can handle double there standard power - sometimes more, but the systems we should put in place to help the engine cope, i.e turbo choice, mapping and cooling are vital.

This i understand, i have seen many home brew turbo builds on here, produce great power, but not last due to poor choices made.

I have been thinking about fitting a quaife for some time now, i guess when i start my build it would be wise to fit one, especially if im aiming higher than 200.

thanks for the link, great info.

[sexy_gt]

Regarding ma boxes. I broke two of them. One was a 4th gear and the other a 3rd gear. My car is circuit use only.

the first box had seen 20+ trackdays N/A and then lasted another 6 with 200@wheels.

second box lasted 4 trackdays till 3rd went, similar power output.

third box was sold after one event and BE was fitted.

i hear from many people the ma box flex.. Having rebuilt several ma and be boxes i can see the difference but is there any proof ma boxes flex?

[axsaxoman]

an LSD is almost a must for a saxo with any form of boost -cos they will spin and thats what does the damage to the boxs --no matter what type -spin then grip --alot of shock loading