General engine questions

Coyoteboy ( snipped-for-privacy@hotmail.com) gurgled happily, sounding much like they were saying :

Which is exactly what I'm planning to do...

Look at the email address...

Megasquirt-UK on Y!Groups, yes, but I've not looked at the web fora for ages.

powerampfreak ( snipped-for-privacy@hotmail.com) gurgled happily, sounding much like they were saying :

So it's shit, then.

And you don't have a clue.

The thread moved on from there. Get over it.

powerampfreak ( snipped-for-privacy@hotmail.com) gurgled happily, sounding much like they were saying :

Where do you fill up?

Adrian skrev:

Adrian, I think I earn the same amount of money in a week as you do in a month. Or possibly two months.... :-)) You seem to have very low skills in reading, since you fail to read (or understand...) the original postings.......

powerampfreak ( snipped-for-privacy@hotmail.com) gurgled happily, sounding much like they were saying :

Firthy and Huge do that "Con-sid-erably richer than YOW" line far better than you.

Yes, yes, we did that already. Remember?

PC Paul skrev:

Increasing fuel pressure by 34% will NOT result in a 34% extra fuel flow through the injector. The flow increases by the squareroot of the increase in flow. Say, ethanol needs 34% extra flow, this comes out to be 1.34 X 1.34 = 1.79, so the fuel pressure has to be increased by 79% to achieve 34% extra fuel. Unfortunately, many fuel pumps doesn't like this.

No, you'd need a bigger pump. You can't always get by with turning it up to

Sounds an incredibly arse about face way of doing it. Injectors need a fair bit of power, and the drivers are already present in the ECU. Easier therefore to modify the ECU.

Dave Plowman (News) ( snipped-for-privacy@davenoise.co.uk) gurgled happily, sounding much like they were saying :

Dunno about that... If it really WAS as simple as "+30% across the range", then it's a decent way to do it - no need to do umpty-seven-thousand maps for everything.

I'm just not sure it is.

But Matey thinks he's got a big payslip, so he MUST be right.

That's because, at least with Firthy, it's actually believeable.

Surely Marshall do a fuel pump regulator?

Oh dear - you lost your credibility right there freak.

Ahah, excellent - classic motors, be interesting to see how you get on with those! I have a friend who is planning the do a beetle and that has some interesting unique areas to work around. If you need to bounce any problems off someone just drop me an email - i enjoy musing on peoples problems!

No, probably not - average fuel trim allowable is normally

The other problem is that not all injectors are plain high impedence ones and can just be PWMd - many OEM injector driver circuits are far from just a switch, instead providing current control and adjustments at varying rpms/duty cycles etc.

The OPs solution is indeed cheap, but it has many flaws due to him apparently not investigating in depth the existing setups possible in OEM ECUs. Its about an A-level electronics project level, and summer homework is due in soon for the new term....?

I'm being mean lol but in all honesty it would could work fairly well with a very basic early 90s EFI system on an un-stressed engine, its WAY lacking on a modern car EFI system and could cause some damage on a high power vehicle if not set up correctly. IMO of course.

Hardly surprising. Most fuel injection systems don't have an extra 30% spare capacity in the duty cycle and the critical point is going to be at peak torque rpm when duty cycle is highest.

This

That's a very silly hypothesis. If you accelerate at part throttle you still accelerate. Why would rpm become limited to a dead stop just because the mixture started to go a bit weak and some power is lost?

Again don't be silly. The engine will continue to increase rpm if the load on the car is less than the power output. Depending on circumstances that could well be the case until the mixture is so weak the engine blows up. The only way to rev limit an engine via fuel supply is a complete cut off until the rpm drops backs below the critical point.

The small fly in the ointment is it isn't going to work for any vehicle that has less than 30% spare capacity in the injector duty cycle.

The way to do this properly is fit injectors with 30% more flow capacity at the same pressure drop. That way the ecu doesn't know anything has changed, no need for electronics, the closed loop lambda will keep mixture at stoichiometric at part throttle and at full throttle the engine will revert to the OE mixture setting.

No it isn't. Modifying ecu's takes a lot of effort and will be a different solution for every vehicle. Piggy back boxes that intercept ecu signals and modify them are a well established tuning principle except that the OP is trying to take it beyond the limits of most standard injectors.

Silly boy. Fluid flow is proportional to the square root of pressure drop rather than to pressure drop itself. With an average FI system running at about 3 bar (43.5 psi) you'd need to up that to 5.4 bar (78 psi) to get the required flow increase. Possible in some situations if the pump is up to it but not recommended for a long and happy pump life.