What size injectors?

[Anlushac11]

I know that on the 2.3L turbos they used 32lb/hr on the 84 Turbo Coupe and the 87-88 used 36lb/hr injectors.

The 84 IIRC ran 10lbs boost and the 86 and later ran 16lbs boost.

Im shooting for 200hp or more from my EFI 200.

Stock pressure IIRC is 42lbs.

Everything Im seeing says I should run 24lb/hr injectors. My gut instinct and what little I know about turbos says to go with about a 36lb/hr injector.

Any advice is appreciated.

 

[XPC66]

If it's only 200hp you shouldn't need any more than 24lb/hr (actual requirement =~18lb/hr= ~193cc/min ) for N/A. For blown you can ramp those up 9%

If you go too big your MLPT may be too long for stable idle.

What sought of boost are you running?

 

[Anlushac11]

Im looking for 8 to 10lbs boost with E85 fuel with a Megasquirt II ECU.

 

[StrangeRanger]

200 HP on 6 injectors?

For boosted applications assume a BSFC of .55 lbs/HP-Hr. So:

200/6 = 33.3 Hp/injector x .55 lbs /HP-Hr. = 18.3 Lbs/hr per injector.

You don't want to push the duty cycle past 90% so

18.3/.9 = 20.35. This would seem to call for 24# injectors which would have a max. duty cycle of:

18.3/24 = 76% which is close enough to the 80% design bogey for all practical purposes.

 

[XPC66]

Im looking for 8 to 10lbs boost with E85 fuel with a Megasquirt II ECU.

OK so on petrol@10lbs boost, with IC, runnig 5800rpm you would be using 20lb/hr (allowing for 9% enrichment on boost).

On E85 you probably need to think in terms of cc/min so as not to confuse the weight difference between petrol and E85. If E85 (25.2mJ/l) is around 73% specific energy by volume of petrol (34.656mJ/l) , logically you would need to up those injectors by 34.656J/25.2 = 38%

i.e. 20lb/hr x 1.38 = 27.51 and adding the old 80% duty cycle = 27.51/0.8 = 34.39 lb/hr rated injector. But on boost you don't run at stoich and with E85 you don't have to enrich so much:

If you were working on AFRs (i.e. equivalence ratios), (winter and summer fuels aside), max power on petrol is around AFR 12.7, E85 on the otherhand has a max power AFR of ~6.97. Adjusting the E85 back to volume equivalence of petrol, assuming it's 6% heavier by mass, would make it 6.97 x 1.06= 7.46. The flow increase over petrol for same power with same air mass would be 12.7/7.46 = 1.72 x 0.73 = 1.25 (1.33 if equal specific gravity = 0.78 )

The difference between the ideal 38% and the AFR based result of 25%-33% tells you that E85 burns at a different rate (better) away from stoich (14.7 petrol, 9.765 E85) compared to petrol. You don't have to enrich E85 % wise as much as petrol to keep things cool under boost. The exhaust volume also increases which isn't a bad thing for a turbo. The downside is going to be the reduction miles/tank.