GR124

I'm building a TRACK ONLY engine
Forged
GTX2860r
E85 (flex fuel)

My car is a 550KG (1200lb) clubman/locost kit car style.
I only want between 250-280 RWHP

My turner recons I can get away with my 640cc injectors?
Im not sure about this

Tell me I don't need bigger injectors? Thoughts please?

Ted75zcar

iTrader: (2)

I recon you might consider a different tuner.

Injector calculator

deezums

iTrader: (3)

If the 640cc is rated at 43.5 PSI as is normal and they are instead ran at 4 bar then it checks out according to the never inaccurate online calculators. More or less what I did with flow force injectors and my old 1.6.

You may need more fuel pump, though. Cheaper, at least.

GR124

I'm running an external DW250 pump

deezums

iTrader: (3)

You would want a manifold referenced fuel pressure since you are cutting it so thin, and you would need to consider the 58PSI + Max Boost PSI pump flow rate. If I remember right a DW200 was too small at ~20PSI boost and ~400WHP, but a DW300 can do it no problem, so I'm sure a DW250 is fine.

GR124

I'm running a Turbosmart 1200 fuel pressure reg.
From what I'm reading if I turn the pressure up on the reg the pump will be working harder. Sounds like I might be like a dog chasing its tail.

deezums

iTrader: (3)

Higher fuel rail pressures might make better fuel atomization and better burn. It's not like 4 bar is a ridiculous pressure, it's what most cars ran before switching to direct injection anyway.

The manufacturers of the pump tell you if the pump can do it. There's no "dog chasing tail." Pretty simple. If you run 4 bar and 20 PSI you need 80 PSI of rail pressure. Add 20% because reasons and you are at 100 PSI.

https://www.deatschwerks.com/sites/w...Tech_Sheet.pdf

This pump flows 190lph at 100PSI and takes ~15 amps to do it. This is three more amps than you would draw at 3 bar rail pressure.190LPH should be good for ~300ish wheel horsepower.

So, buy nothing. Turn the pressure up. Run it. You're within 80% everywhere far as I can see.

GR124

Thank you Deezums for taking the time to go through this. Still looks like it could be close to the max duty cycle for the 640 injectors. I'll do as you suggested and run the engine in on the dyno with the 640s and see how they go when we tune for power.

Arca_ex

iTrader: (2)

You really can't go wrong with just getting high quality bigger injectors like an ID1050x or something. Idle and low load cruising with those are still excellent despite the size and that's really the only trouble area that you used to run into with running injectors that were "too big". I'd much rather have the safety net. I used to run ID1000's on a 133whp naturally aspirated NA8 engine and it ran better and was easier to tune than stock purple NB injectors...

GR124

Not worried about low engine speed stuff, as it's a full time track car. I suppose if I go with your suggestion I am covered when I want more power/mods

DNMakinson

iTrader: (3)

No reason to have a DW 250 and adjustable FPR for those power levels unless you plan to turn up the pressure. Doing so will allow the injectors you have now to work.

Only reason I see is that if you have the ID1000’s AND want to go more power, the tune only needs to be added to up top. Maybe $$ spent for nothing.

GR124

Just to be clear the car is a locost #80 . When my external bosch 044 pump packed it in I bought the DW250. As for the FPR, I have done away with the OE reg and fuel rail.