Fuel injector choice?

[Steve_D]

Going to EFI my Chevy small block and will need 42Lb (420cc) injectors.

Is there a specific make I should go for and where should I buy?

Many thanks
Steve

[stevieturbo]

ebay, fiveomotorsport or racetronix

The Bosch green ( sometimes called Ford SVO ) 42lbs would be the best value.

Edited by stevieturbo on Monday 1st December 22:52

[eliot]

I'm running 60lb Siemens/Mototron injectors in the SBC, so dont narrow your selection down too much if you see a good price on them on something close.

[Steve_D]

eliot said:

I'm running 60lb Siemens/Mototron injectors in the SBC, so dont narrow your selection down too much if you see a good price on them on something close.

Does it not make it difficult to tune the cruise/lower power band if the injectors are larger than they need be?

Will be using Megasquirt.

Steve

[stevieturbo]

Steve_D said:

eliot said:

I'm running 60lb Siemens/Mototron injectors in the SBC, so dont narrow your selection down too much if you see a good price on them on something close.

Does it not make it difficult to tune the cruise/lower power band if the injectors are larger than they need be?

Will be using Megasquirt.

Steve

If the ecu cant control the 60lb Siemens injectors.....its crap. They are bloody excellent injectors.

If you have even the slightest thought that 42lb wont be enough in the future, buy the Siemens.
I thought they were so good...I bought 16 lol

[eliot]

Steve_D said:

eliot said:

I'm running 60lb Siemens/Mototron injectors in the SBC, so dont narrow your selection down too much if you see a good price on them on something close.

Does it not make it difficult to tune the cruise/lower power band if the injectors are larger than they need be?

Will be using Megasquirt.

Steve

I'm running MS and the Siemens injectors no issues at-all with them. Before getting them I checked my pulswidths and they are within spec at Idle - flat out at 8lbs of boost they are only 50% duty cycle - so plenty of scope for power - also running a bosch 044 pump.

http://www.fiveomotorsport.com/Injector_SetsMODS.a...
"High Impedance 60#
Siemens MotoTron
LONG - EV1 connectors"

Ask on the monaro/corvette sections - someone may of upgraded and got a complete set. Roger @ Monkfish may know where some are.

Edited by eliot on Wednesday 3rd December 09:37

[Steve_D]

stevieturbo said:

........If you have even the slightest thought that 42lb wont be enough in the future, buy the Siemens........

When I built it the engine dynoed at 508hp.
I don't expect efi to change that nor do I plan on trying any other mods to increase the power so my understanding is that 42Lb injectors will do the job.

Steve

[Mr2Mike]

stevieturbo said:

If the ecu cant control the 60lb Siemens injectors.....its crap. They are bloody excellent injectors.

It's not a case of not being able to control them, if the injectors are too far oversized the required pulse width at idle becomes comparable to the opening/closing time of the injector and the result is very erratic fuel delivery and poor idle.

[stevieturbo]

Mr2Mike said:

stevieturbo said:

If the ecu cant control the 60lb Siemens injectors.....its crap. They are bloody excellent injectors.

It's not a case of not being able to control them, if the injectors are too far oversized the required pulse width at idle becomes comparable to the opening/closing time of the injector and the result is very erratic fuel delivery and poor idle.

It is...some ecu's have better low end resolution than others in terms of control too. And the Siemens are superb injectors.

Ive even heard of guys using these on 1.3 4cyl engines with zero problems. They really are good.



At 508bhp...Id go for the extra headroom, and use the Siemens, even if the 42lbs wold be fine.

[eliot]

Mr2Mike said:

stevieturbo said:

If the ecu cant control the 60lb Siemens injectors.....its crap. They are bloody excellent injectors.

It's not a case of not being able to control them, if the injectors are too far oversized the required pulse width at idle becomes comparable to the opening/closing time of the injector and the result is very erratic fuel delivery and poor idle.

Agreed in principle - but I have a SBC, with Megaquirt and those injectors and you can tune the idle pulswidths (they are low admitedly - but it works)
Steve, if your'e pushing 500BHP - I would look for a larger injecor. I've dyno'd mine and it has somewhere between 300-400 bhp and 400-500ft-lb (all on the same dyno!) and the 60's are 50% duty cycle at that power level.

[GreenV8S]

stevieturbo said:

Ive even heard of guys using these on 1.3 4cyl engines with zero problems. They really are good.

How low would you let the pulse width go before you consider the injectors are oversized?

[stevieturbo]

There is no definative answer.

Some ecu's/engines could cope with 1 injector at say 1.0ms, yet another combo with same size, different brand of injector wouldnt even run.

The Siemens really are a very versatile injector. I could have chose several options on my car, and choosing 16 injectors was most definately not the cheapest route.
But they just work so well, it seemed all other options would just be second best.

[eliot]

I think my idle PW is around 1.3 ms. Basicly, I used the megasquirt stimulator with the current 26lb map, changed the injectors to 60lb turned the revs down to 800rpm and noted the pulsewidth.

Here's a random log I just pulled up at the of a run before turning off, pulsewidth is shown as 2.2 - which I think includes the 1ms opening time - but anyway its a 350 chevy with 60lbs mototrons on MS1 - which has far lower resolution than MS2. You can see my idle is 13.3AFR - the iron chevys dont like a lean idle, but it will go down to 14.7 as I tried it once for the MOT for a giggle.

http://www.mez.co.uk/graphics/idle.png