Race Engine Forum UK

Hello

My car is a road/hill climb/sprint car. Its a Mk2 Uno turbo 1372cc. I would like to increase the fuelling. Will an adjustable fuel pressure regulator, higher flow injectors and a cam with more lift/duration achieve this?

At 1bar boost A/F is 13.1

Thanks

Liam

the idea of a cam change? This will induce more air but it might simply go over lean. It is on LE Jetronic?

An adjustable regulator will enrich but I would suggest do not increase the injector rail pressure more than 3-5psi.

Bigger injectors? Well here you really need to look up an injector sizing chart. I doubt it will work. If you increase the injector size for same fuel pressure they may not atomise properly..

I would go for the adjustable regulator. You need to get a 0-50psi fuel pressure gauge and measure the present idle fuel pressure, take it up by 3 psi and see what happens.

G

Hello Guy

the idea of the cam change would be to increase air to match the fuel increase of the regulator and injectors. I guess I'm trying to increase fuel and air with a result in more power (subject of thread changed)

System is L3.1 Jetronic (a manual I have says fuel pressure is 6.0bars maximum)

Is there a chance that the factory fuel pressure regulator fitted is out of calibration and not doing its job? Any one know what the factory fuel pressure setting is?

I thought higher flow injectors in conjunction with the higher fuel pressure would achieve more fuel?

Will increasing the fuel pressure make it run rich at low/idle revs?

Liam

6 bar is not the injection rail pressure it is the pump delivery pressure!

On an atmo engine the inj rail pressure is nearly always around 45 psi (3.1 bar).

On a turbo unit the rail pressure (which supplies the injectors) goes up according to boost (or at least needs to) so 45 psi at idle - no boost - would typically rise to 45 +13 psi injection pressure at max boost if the max boost was 13psi.

I recently saw a very nice electric inj pressure gauge by Stack mounted in the dash of Andy Wright's 16v Evo 2 Integrale. This is a worthwhile investment for you.

The purpose of changing the cam setup btw is to induce more air and potentially more power - but without extra fuel injected the engine will simply either detonate or at best give less power. Thus - with a more powerful cam setu - more fuel must be injected.

The graph attached shows you an optimum Lambda curve by rpm and power. Atmo or turbocharged there is no reason whatever to do deviate from the fuelling indicated, though it is true that if the engine starts to detonate you have to pile in more fuel. You also have to retard the igntion. And mighty quick. Better though, to avoid a detonation condition altogether. On turbo units it is induced by oer-hot engine, too hot (over 45 deg C) intake air, too much ignition, over-lean, exhaust back pressure (usually due to a second-rate exhaust manifold) too low grade fuel, too high static CR etc etc etc.


G

Going to an aftermarket standalone ECU or a sophisticated piggy back (Dastek, EcuMaster DET 3, etc.) would give you control of just about all the components responsible for fuelling, ignition and boost. Set up properly, it'd be the safe way to go. It'll involve a little work and a lot of money, or a lot of work and less money. It'll never be cheap.

Cams designed for naturally aspirated engines often won't behave as expected in turbocharged engines, so I'd be inclined to leave the cam as is for now.

Thanks Guy and Fingers99

Think I might go down the stand alone management route and take it from there.

Thanks again

Liam

Slim wrote:Thanks Guy and Fingers99

Think I might go down the stand alone management route and take it from there.

Don't rule out Megasquirt -- it's likely to be something of an assault course unless someone has a base map and can advise you, but kits of parts from the States are about £200.

Fingers99

Is Megasquirt classed as a piggy back or stand alone system? I was looking into the Megasquirt systems last night, do you know much about them?

Liam

They're stand alone.

I don't know a lot about them, just been reading around, etc. I'm going to have to make the same kind of decision with the MR2 turbo soon: can't have my 20 year old £670 car being beaten up by new Porsche Boxters and 3.2 Audis!

Lots of Megasquirt forums, so should be worthwhile posting there.

There's an interesting thread in the Cinquecento/Seicento section of FF about the Det3, which, in one mode, uses very little of the original ECU inputs. It's a Polish development, and Poland is small Fiat heaven.

Worthwhile seeing if someone who knows what they're doing is prepared to do the set up. Over here, there are RRs (including one Guy favours) prepared to set up Megasquirted cars, but there's still a lot of snobbery and "not sold here" about, as well as bona fide chumps.

Fingers

Thanks for the advice

Liam

Just as a further comment, you can actually run Megasquirt as a 'piggyback' system to drive a 5th injector or another row of injectors to provide controlled enrichment to the existing system.

Hi Simon

Thank you for your comment. I would like to control both fuel and ignition. The ideal scenario would be to MAP the existing system but sadly this is not possible.

Liam

I'm now researching Megasquirt via one of the forums. Hopefully I can find someone whom has used it successfully on the same car as mine, and willing to help.

Liam

There is a topic on this system in the announcements in this section too.

GC

Thank you Guy.

I'll have a read of that.

Liam