I reckon you would get a lot more power running ITB's or bike carbs than a larger throttle body from an audi 80. 3.5" exhaust sounds a touch on the big side. TBH I would look at actually calculating the exhaust size that you require for the engine you are building rather than just deciding that you want a big exhaust. Not only will this make your car produce more power and a wider spread of power, particularly with a very wild cam. It will also give you much better marks for your project if you can explain why your exhaust design works.

Nobody.

But if someone can build me a 130 brake 3F motor for a grand, then do it, and I'll buy it, instead of buying another car.

people on here are saying 130 brake is doable, my lectures are saying its do able i think your forgetting flowing the head pipe bending creating the whole exhaust will cost me nothing because college has the equipement, your thinking about getting it all sent off.

answers to a few other questions, i have the GT engine so i wouldnt do a G40 one

i am going for a road legal one but when it comes to MOT keep the old exhaust with cat and all that.

supercharging it is my dream but then i would have to get the G40 bottom

i will look into the audi 80 inlet manifold

cheers for all your help

OK fine. I just can't see you getting 130 bhp from a 3F even if you do all the exhaust making, head work etc yourself.

100 bhp per litre is a great goal. But to be honest the only way I think you'll get it from a 3F for a grand is laughing gas.

Just my input. If others have said its doable, then do it, and prove me wrong!

I was about to add in that once you've done all that then mapping it won't be cheap, but you could probably do that at college. As said though, why one throttle body when you can have 4 lol.

I remember a retro cars article where they made ITBs from old SU carbs (about the best thing for them...). Build yourself a Megasquirt and you'll be laughing.

Not 130 bhp though. That would probably make it the most powerful 3F ever (not counting crazy 10k rpm versions, or bolted on 16v heads).

Edited 11 October, 200718 yr by tobyk

Will be interesting to see what Yoof's 3F makes once we've finished tweaking. I reckon 110-120PS without the nitrous.

Talk of big valve heads on GTs is bollocks. Leave the valves be unless you're wanting to create a crazy rev monster racer. A 2" exhaust should be more than large enough for 130bhp. A 4-branch is a good idea. To get big power you'll need a fairly dirty camshaft, and individual throttle bodies - and I still think you'll struggle to get 130bhp from a 1.3 8v unless you're willing to loose out on driveability.

I have to agree with andy here, your arent going to make 130 bhp even with a nicely ported head. BTW I'm assuming you have a flow bench at your disposal, and Id have said you want a few heads so that you can see what makes good gains. Making a good deal more power through porting is not easy. Have you done any porting work before?

One thing you could do which would probably help the 3F head a fair bit is to mill out new ports at a more downdraught angle and weld up the remainder of the old ones. This makes good power on a number of engines and I have wanted to try it on a polo head for some time. If you do have a flow bench always remember that flow through the head will not be linear when fitted to the block so bench improvements are not neccesarily power improvements.

I didn't say 130bhp was impossible - it is achieveable. You just need a really filthy camshaft, decent induction system and lots of revs. The only downside is you loose torque.

I'm definately going to be watching this project then.

Might be worth looking into Berg cup engines - as posted on another thread they use surprisingly standard components in their 5 figure revs...

This sounds like a good thread to keep up to date with. Fair play.

But who is paying the £1000?

In my opinion you will really struggle to make anything like 130bhp. I'm not saying its impossible either, obviously virtually anything is possible, given enough money, time, and experimentation. The dirtier the cam the more effect tuned headers and inlets have. With a really dirty cam the engine will be really peaky, and in set up you will have huge headaches getting things in tune. You can build an exhaust that should work perfectly acceptably on paper but when you fit it it will need further modification to run correctly.

But if its your project start now you have a few months to get it done from start to finish, you have a reasonable budget, but its not a huge amount of money, you can pick up parts second hand but waiting for parts at the right price further cuts into your project time.

Realistically if you aim for massive power the car will be practically undrivable and it will be a real hassle to finish in time. Although you may have until after christmas to finish your project and that may seem a long time, it really isnt, trust me I've been there.

If I were you I would think about a few good ways you could make good power for little money. Find out if your college has accurate scales, if it does then you can balance your pistons and rods yourself. I very much doubt your college will have a dynamic balancer, so you could send that off to be balanced. That should cost you around £50 for a basic balance, quite a lot more for a knife edge and balance. If you start with a balanced bottom end the engine will rev better, and higher without risk of breaking something. Balancing wont directly give you much gain at all but it gives you a lot more scope for tuning.

once again thanks for all the help i dont know how this 130 bhp came about, i never mentioned it people were saying 130 bp and 100 bhp but i guess someone mentioned it and it carried on from there, i will try abnd keep this updated but i dont think the project will be nearing completeion before christmas so i may start a new thred with the same title and let you know how it when but keep the advice coming and i will try and put some of it in practice cheers

LOL few comments made me laff then!! (not urs tho mate )

any way.... i have a Supercharged 3F and i can tell u NOW that it has cost SOOOO much LESS than 1k !! haha

dunno where half u lot get you are ideas/money ideas from!

if u wanna chat mate, drop me a PM, I'm doing HND in Motorsprt Engineering too, love it, got quite a few people u can talk to aswell - as i dont claim i know it all...

any way! good luck with the project, 130bhp is a good aim, and I'm sure u will get it NO problem mate!

Edited 15 October, 200718 yr by PoloKris

Have you got your charged 3F up and running properly now?

well i will be getting the cam and pulley so thats a bit of my budget gone, any one have an idea on how much a G40 bottom end, ECU and charger would cost?

Absolutely anywhere between £500 and a grand...

Have you got your charged 3F up and running properly now?

its about 90% fine yer! its been on since 19th August... and it aint driven slow....

Sorry to bring up a month old thread but I think this is quite interesting.

I did a bit of thinking about this sometime ago.

This is what I would do:

1.3 engine

Strip engine.

Skim the pistons to reduce top ring land crevice volume.

Skim block to bring C:R to ~ 12.5:1

Full bottom end balance and flywheel lightening.

Full blue printed bottom end.

Build pitot style flow bench for £20 odd.

Get 1.0 polo head.

fit 38mm inlet valves with new guides, 3 angle seats etc

make rubber casts of ports, use to make plaster cast copy head. Modify and flow on bench.

Transfer plaster model port shape to cylinder head.

After market cam 280*+

MK2 polo dizzy. Re-curve with different springs etc

Make manifold and fit 400cc bike carbs with custom airbox.

Calculate inlet length for ram effect at peak torque rpm.

Build exhaust manifold 4-1, again calculate length for maximum savaging at peak torque rpm.

With all that, about 8000rpm and some dyno tuning I think you could reach 130BHP naturally aspired.

If you do the work yourself and have good blagging skills I think you could do this on budget.

We all know superchargers and turbos aren't really tuning. It's cheating.

EDIT: I though this was a month old not 3 years old. Ooops.

Edited 14 November, 200916 yr by varnish

he's probably finished college by now lol

2 years, one month lol. But still, it's still do able i think.

I quit my job and I'm now doing a degree in motorsport engineering.

If I get the chance I will build that engine.

I'd probably put in a wind-age tray as well, as I feel dry sumping would push you over the £1000 limit.

I feel that the way to make the power is with good head modifications.

The standard heads don't flow very well, with no increase in flow after 6mm valve lift.

The 1.3 ports are a little too big I feel. With a 1.0 head you have a better starting point as you will have more scope to change the size and shape of the ports.

If you look at the carbon deposits on a cylinder head you can see where there is incomplete combustion:

That is all around the exhaust valve and the gap between the piston and cylinder wall.

I feel that the quality of combustion could be improved with some wet flow testing to move the fuel spray away from the exhaust valve. Also by reducing the volume between the piston and cylinder wall by reducing the height of the piston to bring it closer to the top piston ring.

With the combustion chamber being in the piston the pistons are quite tall, I feel this contributes to incomplete combustion.

The ports are also quite straight. It would be interesting to build in swirl or tumble to the ports and see how this affects combustion quality.

Where are you studying motorsport engineering?

Castle combe race track.

It's run by Bath Uni, but our facility is actually on the circuit.

What's the course like? Also I thought that facility was ran by Wiltshire College, unless they dropped it (which could happen).

Yeah, we're students at wiltshire college, bath uni and castle combe.

So we get to use facilities at all sites, and get in free to events at castle combe.

if you can get on a cnc milling machine why not think about downdraughting the head? improve flow on the dead side of the valve? if you machine it out you can press fit/weld in some tubes and put in some new seats, then just flow between the 2. you might need to cut a hole in the bonnet but you could run it on bike carbs. that with a hairy cam and revs will put the bhp figures well up there

if you can get on a cnc milling machine why not think about downdraughting the head? improve flow on the dead side of the valve? if you machine it out you can press fit/weld in some tubes and put in some new seats, then just flow between the 2. you might need to cut a hole in the bonnet but you could run it on bike carbs. that with a hairy cam and revs will put the bhp figures well up there

That is an option. An interference fit manifold would be an interesting design too.

You would have to compare a ported head to a down draught head.

I don't know what you mean when you say "flow between the 2".