exhausts?

hi im getting a custom exhaust made from the turbo onwards just a couple of questions before i get back in touch with the bloke
1)whats the best bore size i was thinking about 3"?
2)ive seen a race alpine with the silencer mounted where the spare wheel goes is this a wise move ?the only benefits i can see from this is there wont be any heat near the intercooler

thanks steve

Why are you getting a custom exhaust made??? That sounds like a waste of money that you'll need to spend on repairs when your GTA starts breaking down David does a range of purpose built exhausts that will bolt on and are already proven.

David does a range of purpose built exhausts that will bolt on and are already proven.

They do do the job really well ,haven't stopped since I fitted it ,tho the neighbours are a less impressed as is my bank manager ,but he's always like that .

On the subject of silencers......you dont want any!

but he doesnt do a turbo downpipe or does he?the thing is this bloke(zorstec)has done loads of cars for my family,tr8,rx7.starlet gtt etc and the more i get done with him the cheaper it becomes i also want a bigger bore than 2 1/2" and i also want him to look at the manifolds and see what he can do with them and at what cost i will see what he has to say first and go from there

The standard turbo downpipe on the car is quite well designed and wont restrict the outlet at all......of course if youre planning on fitting a massive turbo at the same time then you may need to increase the size of the down pipe. If your friend can do manifolds I suspect he would get quite a few orders from people in the club (including me!) but I suspect you are talking serious expense. Before you go rushing into all this I would recommend ringing David and seeking some advice.
By the way....are you planning on using it as a daily driver???

the cars summer only and in that time it will be going to yorkdragway and maybe the odd trackday if i can get my asp into gear andy at zorstec built a full system for my dads tr8 that included tubular manifolds and of the top of my head i think he charged around 5-600 quid for his manifolds im not purchasing the manifolds just going to enquire about them and see what he has to say regarding price etc so i take it no one does tubular manifolds for the gta?as for the down pipe im sure dave g has one on his gta?i will be purchasing a bigger turbo but not sure which one to get at the moment i will keep you all informed about the manifolds
cheers steve

If you change the manifolds then you need to make a new 2 into 1 turbo back plate too. The original manifolds have flexi expansion joints because they both eventually meet up together at the turbo. If you make new manifolds without this they will crack, no matter how good a welder you are!

If you want to spend that much money on manifolds and fabrication, better to go the whole hog and run twin turbos.

As for the downpipe, its 2.5" as standard. The wastegate housing outlet on the turbo is only 2". You have to remember the system is very short so the 2.5" diameter doesn't cause the a problem. 3" won't actually fit on the back of the turbo housing. It would need to use a Lotus/Cosworth turbine housing with a complete new downpipe and different 3 bolt flange.

This the problem with GTA's. Nothing is simple. If you want loads and loads of power, absolutely everything needs to be changed!

I have a single exit exhaust on the left hand side of the car, and it is 2.5" throughout.

I have a system designed using larger mandrel manifolds, but it will relocate the turbo to a completely different position. This is what I am going to be doing on the yellow car.

hi dave if you was to use a stabaliser on the turbo(like some cosworths)would this stop the pipes from cracking these cars are a right pain in the asp to get power out of if only they were as simple as a cossie

Its not the flexing thats the problem. If you think about the layout, both manifolds come together and join at the turbo and this would be a completely rigid structure if you had no expansion joints. So when it heats up its most likely the joints on the headers will crack as they have nowhere to expand. You could fit stainless flexi joints as you find on the downpipes on most FWD cars.

The other problem with doing manifolds on the GTA is they have loads of bolted joints for a reason, to make sure they can be adjusted to fit properly. If you make rigid tubular ones, you have to hope they terminate at just the right angle to meet the turbo and vice versa, sit correctly on the heads, otherwise they are going to blow and there will be nothing you can do about it.

There are no other V6 engines that are turbocharged on the market that have the turbo centralised between the V. The other cars are the old 300xz Z31 and Buick Regal V6 turbos, but both of these cars have the turbo mounted on one cylinder head, with a link pipe from the other head going to it. Far easier to make, but again restrictive in power due to the massive unequal lengths, and if you were going to the hassle of making that kind of system, you may as well fit a turbo on the other side.

Supercharging would really suit the GTA. Sorts out the exhaust restriction, no lag, less underbonnet heat, and less emphasis on hot air going into the engine.

How difficult would it be to put a blower on an Atmo ? I s'pose its the intake position , but sounds like a bloody good idea
Always loved the MAD MAX look GTA Interceptor

You would have to change the carbs to blow though items, or upgrade the seals on the existing units. Fit a rising rate fuel regulator and change the igntion curve.

There was an A310 done many years ago, and it made 253PS at only 5.5psi. Used standard compression, GT pack cams.

[Alpineandy]

You would have to change the carbs to blow though items, or upgrade the seals on the existing units.

Injection would be a better Idea.

You would have to change the carbs to blow though items, or upgrade the seals on the existing units.

Injection would be a better Idea.

Its an oddfire engine, with offset cam timing. Very difficult and very expensive to sort out.

[Alpineandy]

Injection would be a better Idea.

Its an oddfire engine, with offset cam timing. Very difficult and very expensive to sort out.

I was thinking of your 'coming attraction' new ecu.