Injector size ?

[quint22cp]

I have a 1988 3.2 that I have just rebuilt to 3.5, other mods are:-

SSI type heat-exchangers,
DC20 cam,
Enlarged throttle body,
Twin plug,
SDS crank fire EFI system,

Do I need to go up an injector size or will the stock 3.2 injectors cope ?

If so what size ?

[STROSEK]

What will your projected horsepower be? I have software that will calculate your optimum injector size. I would be more then happy to plug the numbers in for you.

[quint22cp]

Thanks STROSEK.

I was thinking I would be looking at 260 (flywheel) hp with this set up.

[STROSEK]

Hi, I came out with between 26 and 30. If it was me I would go with 27 or 28 and that's calculated at 3 bar or 43.5 Lbs of fuel pressure. You could always buy an adjustable pressure fuel regulator to fine tune your engine and even get a little more out of the injectors you have now ( assuming they're not too small).

Here's a little info to help you do some calculations of your own. I used software and then this formula to confirm my findings.


First you have to know your engines "efficiency number" known as BSFC.
Here is some target BSFC numbers.
Professional racing engine 0.40
High compression engine 0.50 (0.55 would be about right for you)
Low compression engine 0.60
Turbo/Super charged engine 0.65
If you know your engines Hp use this formula to determine your injector size

Injector Size= Engine Hp x BSFC over
# of cylinders x 0.8

To convert from lbs/hr to metric cc/min use this formula

lbs/hr x 10,5 = cc/min


If you do need injectors they are plentiful and cheap on ebay.

Hope this information was helpful.

[quint22cp]

Thanks for this STROSEK.

I had a look around the net for some flow information on injectors and found a few good sites and some confusing information.

My present injectors are Bosch 280-150-158 and they flow 21.8 lbs (229cc).

I figured that as my engine was close to the spec of a 964 I could use 964 injectors, if they fit a 930 fuel rail. Looking at the spec on these has now got me really confused.

964 - Bosch 280-150-731 and they flow 18.45 lbs (194cc).

I would have thought the bigger engined 964 would have bigger injectors


Has anyone got anymore injector part numbers that flow 28 lbs and will fit a 930 fuel rail and inlet manifold ?

[STROSEK]

I just built a 3.8 monster motor and just purchased new injectors for it. I have a set of fresh stock 964 injectors that have been flow tested and back-flushed with all new seals. I was about to list them for sale on ebay, if your interested I would be willing to sell them to you for a good price. They're 100%. PM me if your interested.

Thanks!