5 bike carbs?

[4v6]

Originally Posted by Gaz

Originally I was wanting to fit a 5 cylinder 20valve turbo engine to my car.. but when i saw the 2.5 Nasp lump for sale i went for that instead.

I do scratch my head and wonder 'WHY?' sometimes, esp when looking at 20vcqdriver's turbo install, i think i'll have fun trying to reach 200bhp from my 2.5L.

How exactly i'm going to achieve that i don't know, but i'm hoping with a fast road cam i should see about 190bhp, Any ideas tho how i might take it from there to 200brake??

Well you already have the main item covered- thats the modified head.

In getting extra power youre basically playing a game of "chase the restriction".
Because youve got a 10 valve head (thats two ports per cylinder) youve got a restriction in the actual design, although youve obviously had the benefits of the modifier at work on those ports to make them more efficient.
Even so, its not ever going to approach the flow potential of the 4 valve heads- so if you want to stay N/A thats where id be going, unless you really want to keep it 10 valves of course.

Camshafts going to be a trade off- aint it always so, whereby youll lose torque low down for a possible gain in power further up the rpm range.
In any case id suspect the camshaft you have already is an optimal grind for that engine so probably little to gain for a lot of outlay.

You could go for something like a vortex supercharger install to give you some positve boost pressure which would allow you to get to 200bhp and most probably some way beyond it, without the plumbing issues of the turbo install, thatd be a fairly unique install also, or maybe a nitrous install for a temporary kick in the pants.

Beyond the obvious stuff like a less restrictive air filter, exhaust and optimised injection and ignition timing i think youre going to struggle to hit 200bhp- short of a hike in rpm to get more work done in the same time, but again thats dependent on cylinder head airflow, and the 2 port head wont go there without some boosted help i think.

Votex Audi GT5-s from the 80's made iirc 160bhp from a modified 1921cc wn code engine(bored to 1933) but that was heavily breathed on and again its a two valve head design.
If the 20 valve design had been available they could well have been knocking on the 200bhp door.

[20vcqdriver]

The 2.5 GTi engine was an excellent conversion at the time and was more about torque than outright power. At the end of the day it is torque that gives you great in gear acceleration which is what you are after not a load of bhp and no torque. The 2.5 GTi engine used the standard KV cam and fitting a Shrick will give more power and torque but higher up the rev range. If you can live with that then it should be capable of getting to 190bhp. After that you need to look at fitting a bespoke injection system and getting it accurately mapped on a rolling road etc. It should with a decent exhaust and work to match the inlet easily reach over 200bhp with around 190lb/ft.
The turbo conversion was a nightmare and needed some ingenious solutions and is still in development as intercooler too small. It is the torque of this engine that really impresses. Presently producing around 250bhp and 280lb/ft. In gear acceleration which is the important on road figure is spectacular. 50-70 in 5th in 4.8seconds and in 4th it comes down to 3.6secs. I'd go for good torque every time in a road car.....

[moomin]

Originally Posted by Gaz

Any ideas tho how i might take it from there to 200brake??

nitrous?