| Page: |
| Home > Technical Chat > FPR postion on EFi | |||||||
 1434 Posts Member #: 8466 Post Whore Mansfield |
18th Sep, 2014 at 05:43:50pm
Can I install my 3.5 bar fuel pressure regulator at the rear of the car next to the fuel pump and just run 1 fuel line to the fuel rail. This will be Naturally aspirated so no pressure signal will be required and the other end of the rail will just be capped off.
Class C 3rd Place Avon 2011 14.18 @101mph |
||||||
|
1267 Posts Member #: 831 Post Whore Montreal, Canada |
18th Sep, 2014 at 05:50:57pm
You still need the manifold pressure reference even on an N/A engine. You may not have boost but you have vacuum so you need the reduced fuel pressure at low load. |
||||||
 9502 Posts Member #: 1023 Post Whore Doncaster, South Yorkshire |
18th Sep, 2014 at 05:59:13pm
This is how modern audis do it ( done a search maybe not all, but the a4 quattro for sure ), they run 4bar with no fuel rail return not sure if its vac referenced or not
Edited by Brett on 18th Sep, 2014. Yes i moved to the darkside |
||||||
|
3588 Posts Member #: 655 Post Whore Northern Ireland |
18th Sep, 2014 at 06:02:36pm
On 18th Sep, 2014 alaskanow0 said:
Can I install my 3.5 bar fuel pressure regulator at the rear of the car next to the fuel pump and just run 1 fuel line to the fuel rail. This will be Naturally aspirated so no pressure signal will be required and the other end of the rail will just be capped off. I'm trying to save weight and cost of fancy hose & fittings. I was thinking AN6 (8mm ID) from the pump. Any body ran Teflon fuel lines inside the car? Yes you can. Regulator at the rear/in tank is fairly common on modern cars these days. But you'll still need to do the flow/return thing, just at the back of the car as opposed to the front. You are correct, the pressure signal is not required. OEM setups that run this type of configuration tend to run a higher fixed pressure too, 50-60psi is fairly normal. Not essential though. AN6 will easily support any amount of power an A-Series would ever make, even in a dead end configuration. Teflon is recommended ( or hardline ) for lines that run inside the cabin. Do not use rubber etc inside the cabin 9.85 @ 145mph
|
||||||
|
1434 Posts Member #: 8466 Post Whore Mansfield |
18th Sep, 2014 at 06:14:04pm
Thanks guys. I ran this setup prevously without the vacum reference with no problems just reg was in engine bay. Cool I'll crack on then. Class C 3rd Place Avon 2011 14.18 @101mph |
||||||
|
1267 Posts Member #: 831 Post Whore Montreal, Canada |
18th Sep, 2014 at 06:35:26pm
Yes, OEM do this and yes you can also do this. But you have to understand why they do it and what potential problems you'll need to overcome.
|
||||||
|
1434 Posts Member #: 8466 Post Whore Mansfield |
18th Sep, 2014 at 07:22:25pm
So what kind of things will be comprised? Class C 3rd Place Avon 2011 14.18 @101mph |
||||||
|
1267 Posts Member #: 831 Post Whore Montreal, Canada |
18th Sep, 2014 at 07:34:03pm
Shorter pulses at low load/RPM due to the non-referenced regulator and more and inconsistent heat in the fuel due to the non-recirculating long line.
|
||||||
|
1434 Posts Member #: 8466 Post Whore Mansfield |
18th Sep, 2014 at 07:43:25pm
The problem with MAP reference, is I'm running ITB's, so the signal is quite unstable, and effects AFR when connected.
Class C 3rd Place Avon 2011 14.18 @101mph |
||||||
 (2)[/url] by [url=https://www.flickr.com/photos/150672766@N03/]Rod Sugden[/url], on Fli) 5988 Posts Member #: 2024 Formally Retired Rural Suffolk |
19th Sep, 2014 at 08:05:18am
On an OEM setup without any MAP reference to the regulator, the ECU usually still reads MAP so can vary the pulse width for the non-constant pressure across the injectors.
Edited by Rod S on 19th Sep, 2014. Schrödinger's cat - so which one am I ??? |
||||||
|
3588 Posts Member #: 655 Post Whore Northern Ireland |
19th Sep, 2014 at 08:28:52am
On 18th Sep, 2014 jbelanger said:
Yes, OEM do this and yes you can also do this. But you have to understand why they do it and what potential problems you'll need to overcome. Non-referenced regulation is not ideal and a long line of non-returned fuel adds more potential issues due to heat in the fuel and potential vapor lock. But if you think that the compromises are worth it, then go ahead. Just be aware that you are using a compromise not just a different setup. Actually when running, a return style setup will run hotter fuel into the engine than a dead end. The only time the fuel will heat up in a dead end, is when you've stopped. This hot fuel will soon be gone once the engine is started though. Most of the heat in the fuel comes from circulating through hot rails at the engine, plus a little from the pump itself. So running a dead end will result in cooler fuel being injected almost all of the time. I know of some guys pushing 4 figures with dead end setups. I wouldnt do it myself, but I suspect a mini engine isnt really going to require that sort of fuel demand, so 100-200hp or so with a large -6 line...in terms of fuel flow, there is no compromise. And as for hot starts etc, I assume he will be using a programmable ecu, so most ecu's allow a large first injector firing to expel any air in the rails if need be. And as for vac reference, really doesnt matter one bit as far as tuning goes as you'd be tuning with the fixed rail pressure which will be perfectly consistent anyway. IMO there arent as many negatives as some might have you believe. But for same of a few feet of hose ? I'd always prefer to run a return line and mount the FPR either local to or after the rails That said...for handiness on my own V8 with dual injectors, I run one pair of rails dead end and the other full flow. Saved a big mess of hoses under the bonnet. Been like that for several years with never a problem. Until last year the injectors were staged, so my primaries were the dead end ones. Never any vapor lock, hot or cold start problems. The FPR is local to the engine though. After an ecu change this year, I just fire both injectors together instead. 9.85 @ 145mph
|
||||||
 8604 Posts Member #: 573 Formerly Axel Podland |
19th Sep, 2014 at 10:36:54am
If this is a track car then I don't think that there will be a problem. You will have to compensate for the variable differential pressure across the injector in the VE or pulse width table in the ECU.
Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
|
||||||
|
1267 Posts Member #: 831 Post Whore Montreal, Canada |
19th Sep, 2014 at 03:28:53pm
On 19th Sep, 2014 stevieturbo said:
And as for vac reference, really doesnt matter one bit as far as tuning goes as you'd be tuning with the fixed rail pressure which will be perfectly consistent anyway. Of course you tune with the fixed rail pressure and it will be consistent. But if you have largish injectors and good vacuum at idle, you will have very short pulses at idle. And if you don't know your exact injector dead time or have an ECU which can't compensate for non-linearity then you're going to have fun trying to tune around it. Voltage compensation and transitions might also be issues. As for having long initial pulses to clear out any air/vapor, that's nice if it does compensate exactly for all heat soaked and cool starting situation but that's definitely more of an issue on a dead end setup. My point was that using such a setup might be a non-issue and might even have some advantages. But you have to be aware of the potential issues and see if you want to deal with them. A vac referenced and circulating setup may have issues but should be more benign and easier to deal with. |
||||||
|
3588 Posts Member #: 655 Post Whore Northern Ireland |
19th Sep, 2014 at 03:52:42pm
For years ecu's never had any injector dead time info and it never posed a problem. It's a more recent thing.
Edited by stevieturbo on 19th Sep, 2014. 9.85 @ 145mph
|
||||||
| Home > Technical Chat > FPR postion on EFi | |||||||
|
|||||||
| Page: |