tommye

No !!

Yes !!


Tommy

HansB

No, that is not correct.

Flow through the injector is determined by the differential pressure over the injector. Boost pressure will increase fuel pressure, but the MAP will increase with the same amount. The FPR will keep the pressure over the injector fixed.

HansB

Raceboy, you beat me to it. Got distracted by a telephone conversation!

Thom

Yes.
HP talks on here do get confusing as our friends from the US don't seem to measure in the same units as we in Europe.

HansB

I made a similar comment some time ago, got flamed for it, but I agree.

Like I said, 290 Flywheel/Crank HP is close to or a little over the limit.


BTW, the only disadvantage of bigger injectors is that regulating low flows, like idle, becomes more difficult.

Patrick, I am very curious how you will manage with your 1650! s

Thom

Not sure why - everyone has the freedom to measure in wichever units they want.

A figure of 550whp on a Mustang would probably equate to about 400 to 450 bhp (crank). I believe this is about what Corleone's car did on a Rototest.

333pg333

Not quite as curious as I am Hans.
I don't think there will be any issues with the E85 map, but getting good cold start/idle on pump fuel is the challenge. Going with a twin inj setup would be the best in this regard but time and money get involved. We shall see in about 10 days without any more delays.
Perhaps those last 4 words are a little hopefull.

Raceboy

I've tuned Audi 2.2 20v turbo with 1200cc injectors and regular 98octane pump gas and it idled/cruised perfectly @ or near lamba 1. That was with standalone engine management, full sequential. Dunno about other options.

And that was 2.2liters, 5 cylinders, only 0.44 liters of displacement per cylinder.

V2Rocket

those audi 2.2's are practically invincible though

just to clarify: you guys say that FP will increase with boost...would it be necessary for me to get a higher rated FPR? i have the stock 944/951 unit (2.5bar) and assume that would be enough for the 951 injectors...i may end up getting a 3+bar regulator eventually just to be safe with the injectors (give them a little more room in duty cycle) but for now would the 2.5bar suffice?

as for my setup, i will be SC'ing an M44/01, early NA engine. it's got 9.5:1 compression and out of the box ill be running something around 12psi with a big A/W intercooler and probably (m)ethanol injection...

i figured id be asking my important questions here as this is where the masters of boost reside

i know the vast majority have stuck with A/A IC's but if anyone has experience with A/W, i was hoping they could help me with a plumbing question...which would be more efficient at pulling heat out of charged air:

- dedicated cooling system just for the IC with its own heat exchanger, fan and electric waterpump, expansion tank (necessary???)
- running in series with the existing cooling system, with a 951 waterpump feeding into a secondary heat exchanger which leads to the inlet of the IC, with the IC outlet going into the top of the radiator as usual?

Raceboy

Spencer,
If you're going through the hassle of installing A/W intercooling, do it properly, with separate liquid cooling circuit. Otherise you're just adding stress to the stock cooling system that will have to deal with additional heat due to boost (remember the rule of thumb: 1/3 of the energy released in comb. chambers goes to cooling system, 1/3 to exhaust and app. 1/3 to flywheel).

And definitely install 3bar FPR, more is not necessary for start.

V2Rocket

the reason i chose A/W is because there is simply not enough room in an early car without serious sheetmetal modification...the idea of a 951 cooler right up front has crossed my mind several times but i would rather not cut up the front of my car.

all the mods ive done so far have been designed so that they can be undone if necessary to sell the car; for example i removed the seatback from the rear seats but left the bottom in because it would be difficult to reinstall and also acts as good sound insulation. instead i built a panel to cover the seatbottoms and hold some speakers and stuff. in the end i am still down 15lbs, while enjoying some good music (and low road noise)

in order to use a A/W i just need to snake some water lines through existing channels in the body and mount the heat exchanger somewhere where it will get a good airflow, either in front of the radiator (no AC) or (where im more leaning to) in place of the power steering cooling coil (no PS)

your comment about adding stress to the stock cooling system is very good; i have heard from others (namely renegade hybrids, maybe they were just trying to sell me their radiator kit) that the existing cooling system is pretty taxed as is, so i wouldn't want to overstress things. in addition the water being circulated would be a higher average temperature than that of a dedicated cooling circuit as there is much more aluminum thermal mass in the block to transfer heat consistently than there is in the IC...a dedicated cooler would probably keep water temperatures closer to ambient, even if it required more plumbing (dedicated pump)

porschefig

Spencer, cool project!
Good Luck!
I think stock 951 injectors and 3bar fpr should be plenty for 12 psi. SFR uses 951 injectors and a 951 intercooler for thier stage II supercharger kit (8 psi).

V2Rocket

would the 2.5bar suffice for now though? if they flow 36lbs at 2.5bar...i should be well under 300hp and thereby within their limitations unless everything works better than i expect it to lol

thanks for the wellwishing i hope it works at least as well as i expect it to. i have a wonderful resource to help me (all RL!) and a very knowledgeable friend here (sid) so this should be pretty interesting.

i hope you turbo guys dont mind me staying for a little while...and of course ill post pics when things get moving

blown 944

Hans I have had this conversation once before.

I suppose if one wants to simplify to just pressure differential than I could agree. However I have found that there are other forces that contribute and that the 1:1 ratio is not perfect.

You have to take into consideration the specific gravity of the fuel you are using and it's mass along with the kinetic energy that it produces within the fuel rail and at the injector tip against the mass you are injecting into. There is also a Phenomenon that occurs when a valve is shut abruptly that increases the pressure ~3 times the amount of line pressure at the valve head .

This is why I don't feel these charts are accurate.

Coming from a mechanical fuel injection background I have found that injecting pre pressure (blower in my case) and after there was not much difference in the nozzle size.

As to HP claims and whether the stockers will work ...well, dynos are just tuning tools my real test is the quarter mile and my 951 ran over 105 with the stock injectors w/o supplement and that is ~ 290 so pretty close.

I don't think it ideal to run at high pressure and IDC but is possible.

333pg333

Mine will be 3L with full sequential ems. The issue will be to get good idle with these big inj on 98oct pump fuel. Wonder if our pump is the same oct rating as yours?