by David Gentleman » Sat Mar 04, 2006 7:22 pm
I am quite tempted to rig up this system on a spare engine I have here, as I have the suitable turbo, ecu, chargecooler, cams and can sort out the manifolds quite easily.
I could then get the engine on a dyno to measure the power output.
The problem with the GTA, (and we've been over this many times before), is every component is flawed.
For instance, we know to run more boost we need better intercooling/chargecooling, but the standard turbo is very small, so this needs upgrading, but we also know the exhaust is restrictive (and the turbo elbow), so this needs changing too..
Then we can only run upto around 14psi, as this is the factory limit, so we need the ecu, 3 bar map sensor (but also bigger injectors as Renault saw fit to install the minium requirement)
So, now were running say 16-20psi. Depending on what boost level you run (you may want to go higher), this is probably the best setup to retain the original 'punch' of the GTA, without sacrificing drivability. It will still have a massive kick in the pants feel...
The next step, as we are cramming all this boost in, but its not flowing through the engine efficienctly above 4k, is to fit the better cams..
And at this point we are still only about 280-310bhp....
The power band has now shifted about 2k up the rev range, but still dies off around 5k..
Now the exhaust manifolds are the restriction (even the standard manifolds on the atmo are a restriction at 160bhp!)
Problem is, to change to the different manifold system as I mentioned earlier, you need to junk all the decent downpipe and exhaust system purchased previously and go for a complete new one as the turbo is in a completely different place..
Now potential wise, there is no limit. The manifold design I have is much like the single turbo setup on the old Lemans Car PRV turbos, which were 2.0 V6, and ran over 600bhp.
300-400bhp>> depends on boost pressure and turbo choice...but its going to be very laggy, a narrow powerband and still only rev to around 6500 max..
The only restrictions after this is going to be head design/valves/physical strength..
Then the next step is the Laguna V6 engine transplant, race cams for that engine (can't use the 2.5 turbo ones), and the benefit of the lower compression for more boost, bigger valves and ports and increased capacity..
We have been over and over this subject but then until recently it was thought piggybacking wasn't worth the hassle
It would seem to be a worthwhile mod and from what I've read from various sources pretty straightforward .
Should be good to see this in your car later in the year 
