GTA's Achilles Heel ( Devils Advocate )

As the title says, Devils Advocate . To expect 800+ lice burner bhp is ludicrous .My question was really asking why,where ,what are the restictions

Right, to clear it all up I'll list the main points/problems

Inlet valves and heads - fairly good sized valves 44mm in/38mm ex.
Ports are 40mm diameter. As a 2 valve per cylinder engine goes, this is about the same spec as a big valve headed Pinto cylinder chamber.

The biggest valves that can be fitted to this head are 46mm inlet and 39.8mm exhaust, so a slight gain. Ports cannot be opened up widely as there are some water channels running very close to the inlets.

Cams are very mild, only 6.5mm lift with very low duration and overlap. Uprated cams will give a 25% increase in lift and duration so the valves are held open longer and higher.

Throttle body is 55mm, inlet manifold has no restrictions. 55mm throttle body is good for about 22psi of flow through this capacity engine, even if better breathing with cams. Beyond this it begins to create a pressure drop on boost (note all the piping from turbo to inlet should not drop below 55mm to retain this capacity)

Pistons - No problems here, the stroke has been shortedned on the 2,5 engine, but the piston crowns have been increased to compensate. ..but, if you were going to build a super dooper engine, you will probably invest in a forged set of pistons, simply for the sake of it.

Liners - Never any reported problems with cracking. All liners on this engine do not overlap/touch each other, and are thicker on the 2,5 engine, than on the 3.0 A610 engine.

Conrods - Forged as standard.

Turbo - standard or hybrid, feature a turbine housing with a 2.25" max outlet. This will limit power in relation to a Cosworth/Lotus style housing which has a 2.75" outlet and can mount up to a 2.75-3" downpipe.
Turbine housing size is in relation to output power (once manifold problems have been sorted) 0.36 (standard) will flow up to 240bhp, 0.48 housing will flow up to 270, 0.63 will flow up to 370. The larger the housings the more lag. Cosworth type 0.48 will flow up to 290, and 0.63 will flow up to 400 (with matched exhaust) All hybrids will need to have larger compressor wheels to increase flow.

Manifolds - Crap. 3x1.25" primaries leading straight into a 1.65" header to each side of the turbo. Its restrictive in diameter, and in length. Requires free flowing headers, larger bore, finalising in at least 2" diameter, or twin turbos.

Exhaust - Requires 2.5" downpipe at least and free flowing exhaust.

Ecu and injectors - Can only cope with around 250-260bhp of fuel flow. Can only cope with around 16-17psi of boost handling on the map system.

Oil cooler - Would require seperate radiator for high power applications.

Intercooling - Big intercooler/water injection or chargecooling.



If the standard ecu on the GTA was remappable and the injectors were larger there wouldnt be a real problem.

On any other engine, you would concentrate on cooling the boost, running about 20psi, and remapping the standard management.

If the GTA came with a ecu that could be remapped, it would be fairly cheap and easy to do, but because of the limit around 16-17psi, we will never get that extra bulk of power, without changing the ecu completely.

On the R21's they have this more modern type of ecu. They come with 175bhp as standard, but can be wound up to 20-25psi (no cutout limits) and some people are reaping around 230-250 on relatively standard engines. One guy has 284bhp at 22psi on a standard engine bar a larger turbo and remapped standard ecu.

So, even though cams, valves, manifolds will reap more 'natural' power on the GTA, simply concentrating on cooling and mapping with more boost can overcome these deficiencies and get fairly close to the 300bhp level.

Essay over

i never said anything has 280bhp i was just qouting what clee had said in the begining of this thread that 280bhp seems tops for the alpine engine why is it that if big power is ever mentioned people seem to get a bit touchy

I don't think its that people are touchy, its just any big power GTA is only going to make more power after 5500rpm, and less power than a standard 'boosted' GTA below this...

...so to drive on the road, its much for much going to be slower - until you reach 5500......but then, because its an old V6 and probably only going to rev to around 6500 max, that your only going to have a good power band of around 1000rpm...

So do you want to all these things and spend all this money and have the risk of it being slower and harder work to drive?

A GTA is an all round driving experience. Good accelleration, handling, balance etc. I wouldnt want to ruin coming out of a tight corner with no torque and waiting a few eons for the turbo to kick in...Do you?

A solid 300bhp car would be more than enough, and this is what I am aiming for with the new ecu, turbo, chargecooler and trying to retain standard internals.

Where's the clappy smiley Thanks Dr G .
So cooling ,cams and ECU ..........and manifolds

Where's the clappy smiley Thanks Dr G .
So cooling ,cams and ECU ..........and manifolds

..and turbo...we need more boost, so the turbo has to be big enough to flow it. Standard turbo is on its limits at just over standard boost..

..Cams will gain - but it would be nice to gain significant power without pulling the engine apart..


...and manifolds - they really will make it sooooo much laggier.

hi david gentleman

how much bhp with a standard case then

alpinerob

hi david gentleman

how much bhp with a standard case then

alpinerob

More with a Samsonite..

Where's the clappy smiley Thanks Dr G .
So cooling ,cams and ECU ..........and manifolds

..and turbo...we need more boost, so the turbo has to be big enough to flow it. Standard turbo is on its limits at just over standard boost..

..Cams will gain - but it would be nice to gain significant power without pulling the engine apart..


...and manifolds - they really will make it sooooo much laggier.

Yes Turbo as well .He giveth and he taketh away ...............

I'm pretty sure my misfire is down to fueling now .The champ plugs seem ok and the ngk's same .I'm running 16 + psi on a new/std regulator and it's far more pronounced under heavy acceleration .

Its just a old RV8 with a few mods http://www.roverv8engine.co.uk/index3.htm

Have you tried that chemical block sealant yet Mr Jon?

Hi Clee, it arrives tomorrow. Not building my hopes up but will keep you posted!

By the way, message for The Gentleman, any news on the possible engines you may be acquiring???

Yours, as desperate as ever. God, after my bad luck i must really love these crap plastic cars to still be persevereing!

Mr Jon

How do they get 630bhp out of this?

http://www.fa-automobile.com/detail_ven ... d=34&v=681

..thats 24v heads, 3.0l, T3/4 hybrids instead of the normal T25's, twin intercooling and standalone management. They normally run around 1.4 bar boost too..

I don't care about it's spec. It looks awesome!

I'm pretty sure my misfire is down to fueling now .The champ plugs seem ok and the ngk's same .I'm running 16 + psi on a new/std regulator and it's far more pronounced under heavy acceleration .

I have the same problam when running 15/16psi. I get a hesitation at about 4000rpm and a slight misfire from time to time. With the bleed valve shut its gone. I already have a new rear fuel filter so the possibilities are that its either the front filter (good chance as the car improved significantly when I changed the rear one), pump (seems healthy), injectors (possibly as I changed them for 214cc then back again and hadnt exactly looked after the old ones in the meantime) or regulator (who knows!! )
Ive bought a set of 191cc cossie injectors off t'internet for £20 to see if they help at high boost and will do the front fuel filter soonest.