Economy and Injectors

[WetGTR]

The richer mixtures at light loads is most likely to stop the car surging.  This is where a slow speed probe should be used to determine CO and NO to determine the real combustion process.  The higher the RPM the leaner you should be able to make it without surging.  You could try setting your target 14.4-14.7 and see if the car cops it, but you would probably want to do this on the dyno.  You could also enable the lean cruise function.  Talk to your tuner he should be able to guide you.

Spot on rob82!

This is exactly what happens with big cams. Have to find a happy medium

[rob82]

Yep how did you go? Have you installed a O2 sensor? Also what Autronic is it? Those cams do sound rather larger, what is the actual duration (at 50 thou) as I'm guessing 280 is advertised duration? What are the plans from better economy?

[WetGTR]

Yep how did you go?  Have you installed a O2 sensor?  Also what Autronic is it?  Those cams do sound rather larger, what is the actual duration (at 50 thou) as I'm guessing 280 is advertised duration?  What are the plans from better economy?

OK, here is the update.

I rang my tuner, benno.

Firstly my biggest problem is the cams at 280 in & Ex with 10.2 lift are way too big. He has explained this to me before thats why I was looking at other options. He seggested the Tomei Poncams 260 in & ex with 10.25 to replaced my cams. He has just finished a car with a similar turbo to my own which is a T04Z & it produced 400awkw. Mine is at the 412awkw mark atm so not too far off.

Secondly, no point in installing a O2 sensor as he can get better fuel consumption with this turned off & completly running in open loop. He has got be be a gun tuner for this, as I believe most tuners need closed loop to get good fuel economy.

I asked about the twin nossle injectors & they would help but only buy them if you were buying injectors anyway.

Makes more sense now.

BTW I'm running the Autronic SMC ver 1.92

My only problem is if I change my cams, I will need a re-tune. My tuner is in Melbourne and I'm up here in Sunny Queensland.....

Might need a few 20L jerry cans in the boot to make the trip hehehe

[WetGTR]

SK i think is mostly like right and your cams sound a bit big as i'm run a (combine turbos 640hp rating) where the t04z is what more like 800hp so i cant see why your gtr still wouldn't make that sort of hp with smaller cams (i'm run 260 9.15mm in/ex for 397rwkw)

can i ask what boost you run for the 417awkw?

and the lift of the cams?

cheers pete

I run 1.3 bar and just found out my cams lift is 10.2

[rob82]

The way the Autronic fuel injection works is based on VE efficency, so once you actually MAP the ve any non internal changes you make should theoretically make no difference, this is the beauty of the Austronic. This means you can run whatever boost and the fuel curve should look exactly the same.

The better fuel consumption running open loop may be a little detrimental to chamber temp thought. If his target AFR is say 14.7:1 for the points around cruise and the VE is slightly wrong you may be running a little leaner or richer either way is what you want to avoid. The o2 sensor trims both directions as in if it to lean it adds fuel and if it is to rich it takes out fuel. After all thats the reason why ever manufacturer in the world uses an o2 sensor opposed to just running opn loop.

It sounds to me that your not going to lose much power at all whats 10-15kw when you have 400 odd anyway. So its your best bet for better fuel economy.

[WetGTR]

Sounds like the Autronics dosen't do a bad job of things...

What the point of having big cams if you get similar power from smaller cams?

[rob82]

Sounds like the Autronics dosen't do a bad job of things...

What the point of having big cams if you get similar power from smaller cams?

Well thats just it. Go the smaller cam - you might not lose any power at all but will most probably gain better fuel economy. As for the 1000cc injectors I forgot to mention that the bigger the injector the harder it is to control low pulse width fuel flow -as in idle and cruise. If your happy with the current power output a reduction in injector size will most likely result in huge economy gains probly even more so than changing cam size.

[WetGTR]

What size injector would do the job? Keeping in mind 400 odd awkw and not to run them at max duty cycle.

Anything good or bad about sard injectors?

Just asking as they are well priced but I prefer quality items.

[rob82]

For 640 engine horse power you need about a 800cc/min at 85% duty cycle. I'm assuming the current 1000cc injectors are top feed low impedance? Sard are generally consider pretty good we havn't had much trouble with them apart from 1 car. However I find the nismo items have a much better low duty cycle accuracy, however not sure 740cc will get you there it will be very close as the rate flow is always a little more than stated.

Has anyone found the limit of the 740cc/min nismo injectors?

[FATGTS-R]

Interesting stuff. I also have an Autronic SMC ( RB20) and was running standard single pintle GTR injectors.

These have now been swapped out for high imp bosch multi pintle injectors at same capacity and tuner noted he had a lot more precise control with them.

[WetGTR]

For 640 engine horse power you need about a 800cc/min at 85% duty cycle.  I'm assuming the current 1000cc injectors are top feed low impedance?  Sard are generally consider pretty good we havn't had much trouble with them apart from 1 car.  However I find the nismo items have a much better low duty cycle accuracy, however not sure 740cc will get you there it will be very close as the rate flow is always a little more than stated.  

Has anyone found the limit of the 740cc/min nismo injectors?

You would be assuming correctly - top feed low impedance type.

[WetGTR]

Interesting stuff. I also have an Autronic SMC ( RB20) and was running standard single pintle GTR injectors.

These have now been swapped out for high imp bosch multi pintle injectors at same capacity and tuner noted he had a lot more precise control with them.

This is good!! What results did you obtain, eg more economy, better midrage power, better drivablity, etc.

This is the perfect before & after for injectors.

BTW what brand were they before ?

[pnblight]

700cc sard in my gtr run at 75% on std fuel pressure reg at 397rwkw so 700cc sards would serve you just fine

[Cubes]

Grab the sard twin hole squirters.

No doubt will help with atomization for low pulse.

[WetGTR]

My arm is getting twisted towards the Sard's. Nice options from people in the know and nice price.

Might go the 800cc twin spray type, just in case I need the extra.

Unless this is bad.....

I was also thinking the Nismo items but couldn't find them at Greenline or Nengun in the 740cc range for the RB26.

Looked at the Power Enterprise ones but very expensive - Sard 800cc twin$645 verses the Power Enterprise 1000cc twin $1400