87 325(e) - fuel injector for adjustable fuel regulator?

[cirrusblue]

Hello R3V - yes, I have an e... but it's a champ, it's chipped, burns "0" oil at 200K and I'm sentimental about it... it's really solid.

But here's my point - I wanted to experiment with an adjustable fuel regulator and injector set to see how I might be able to tune a little bit. I know a seasoned mechanic who's had soem good results doing this.

But I wanted to know if anyone has done this or has any recomendations for fuel injectors for an e that may get a little pressure update - I think the e injectors are rated for 2.5 vs. 3, but I'm new to this.

Looking for some thoughts, and I know it's an e - so it's not a drag racer, but I like how it drives and I'm going to have it a long time so i do little things here and there...

thank you!

- CB

[Kershaw]

What's your end goal? More horsepower? There's probably a better way to achieve that. an i top end swap should not take you more than a weekend.

But, if you just bought the car, just like a house, it's probably best to wait for a year before doing any major modifications. Just do the basic routine maintenance and get to learn the car.

[cirrusblue]

Hello Kershaw - no it was my father's car and then a few years ago became my car... so I know every oil change since 87 with this thing. I've gone over every inch of it by hand many times.

The end goal really is just to have it be the most optimized version solid runner that I can make it. Full disclosure is I do minor work myself, but have an indy shop that does my engine work... the owner of the shop is a respected guy who said he's done this many times, esp. back in teh day and I'd get a little more power. he kind of sold me on it since he had done it so many times. But you know how people are...

the conforti chip made a big difference, totaly replacing the intake leaks, afm and all of that made a difference... so it' smore of atweak thing... plus I'd like new injectors anyway as i'm sure my old ones are pretty dirty...

since the regulator is adjustable, I dont have to run it that rich if I dont' end up wanting to..

that's the reason.. a subtle tweak...

[nando]

it's not going to work. in fact, it's a really bad idea.

First of all, since it has an O2 sensor, it will run in closed loop. Any fuel you add will just be subtracted out by the computer as it adapts (both short and long term trims).

Second, when you change the pressure the injector runs at, you change the slope of the injector curve. Basically, for a given pulsewidth and fuel pressure, the amount of fuel that flows out can be known. This is the foundation for EFI. The DME has a factor built into it for how much fuel the injectors flow, but now you are dicking around with it by using an AFPR. So now the injector response does not match what the DME calculates, which will throw the EFI algorithm out of wack (further complicating the fact that it's trying to dial back the fuel with O2 trims).

Thirdly, you're trying to make it run richer everywhere, not just at WOT where it will help. And since you already have a chip, the fuel will basically already be optimized anyway, so it's pointless to increase it further.

Basically - do yourself a favor and sell the AFPR or chuck it in the trash. it's not a valid way of tuning and will cause more issues than it's worth. the eta is tuned for a 2.5 bar fuel pressure and it works just fine like that. the stock injectors are more than adequate for the eta so "upgrading" those is also pointless. Just get them cleaned and call it a day.

also, few mechanics know anything about tuning, so I'd take any advice from somebody recommending that you "tune" it by randomly bumping up fuel pressure with a mountain of salt.

[Kershaw]

You're injectors are low impedance injectors, I'm not sure just swapping in larger injectors (the ones commonly found around here anyway) will work, since they are high impedance injectors.

Just tweaking the fuel delivery might not be a great idea. It doesn't have carbs. And the computer (digital motor electronics/dme) is constantly trying to achieve the best air/fuel ratio it can.

[modernist]

Here is a huge spreadsheet of Bosch injector specs, if you're still curious.

But to quote Charles O. Probst's Bosch Fuel Injection and Engine Management,

"Remember, Bosch is already pretty good at this stuff."

[cirrusblue]

I'll admit, before I was told by this mechanic that he'd done it a bunch, even with stock injectors - I would not have believed it. I"m getting less interested in doing it now, it does seem against the motronic concept...

Bav Auto has this item though and they say it fits 325e...

http://www.bavauto.com/Assets/inst_pages/ins062.pdf

Overall... I guess if I don't hear from anyone who's done it... and done it sucessufully who seems knowledgeable it seems kind of unadvisable now...

[Kershaw]

That's more of a thing for turbocharged cars.

[nando]

you can put high impedance injectors in a low impedance system without damaging anything, it's low impedance injectors that will fry a high impedance DME. Either way, still no point to doing so on a stock engine.

[cirrusblue]

ok, I'll consider myself disuaded :)