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Ok, went out and dynoed the "big twins" again tonight:

21.5 psi, or what I run on pump gas on the street: 698/551

28 psi, or my hold-onto-your-balls setting: 780/625


I could use some thought on the following problem: I didn't spray it tonight, as I was getting baselines for all turbo. A/F held pretty close to 12:1 on the low boost, but the high boost caused a steady lean-out towards redline, as high as 13:1 on some. EGTs were fine, of course - it was just a one gear pull. Normally, this is a standard indicator of lack of injector, except that I am running 850s. Fuel pressure is at the 43 psi static standard, and I am getting a perfect 1:1 rise. It's almost like I am beyond the map sensor reading capability, but I'm not of course. Ideas?
 

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780rwhp is where 850cc are limited to provide. anything over 850cc will be hard to get clean tuning. is there 850cc or bigger vpc chip from hks? well, you could push higher fuel pressure but it's safer to go with bigger injectors. nice dyno number. about what rpm do you get full boost? is there bigger twin turbo kit from hks?
 

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Hey Darren. Have you checked the voltage on your fuel pumps? Dave was have problems with his..was not getting full FP at WOT. He was maxxing out at 50 psi(from 40 static). He yanked his stockers and put in some Walboro's(sp?) I don't think he needed to but he wanted to be safe. I think his wiring was faulty. What kind of A/F wide band did you use?

Was this done with the bigger housings(.87s)? Any difference on the spool up?


Scott

Peace
 
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v8huntr said:
780rwhp is where 850cc are limited to provide. anything over 850cc will be hard to get clean tuning. is there 850cc or bigger vpc chip from hks? well, you could push higher fuel pressure but it's safer to go with bigger injectors. nice dyno number. about what rpm do you get full boost? is there bigger twin turbo kit from hks?
I guess I could go to 1000cc injectors, but I think I will wait to see how the AEM ECU comes out. HKS does not offer a solution VPC-wise. And yes, there is really no limit to how big you want the twins to be.

Scott, I recorded a perfect rise in fuel pressure for boost, so that's not the case. I got 5.0 kg/cm^2 at peak boost.
 

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Could you be maxing out the ECU's ability to read more airflow? (850cc / 550cc) * 520 = 803 (of course, this assumes that airflow is proportional to HP, but I'd imagine its not completely linear). That is, assuming it can't read more than 520 rwhp on stock injectors, I really have no idea if that is the case or not. Either way you probably have pretty high duty cycles, but what do I know....
 

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I thought u sold the beast? Is this a new one? Are u still on the stock ECU? Also what type of wiring and what amperage relays do u have. I was running lean at high boost. Turns out I burned out a fuel pump. My relays couldnt handle the amperage and were constantly clicking on and off. I am pretty sure that aided in the pumps demise. ( I also didnt keep a 1/4 tank at all times). If u have the stock Supra pumps and they arent getting the correct amperage and voltage the could be in 9v vs 12v mode also.

Oh, congrats on the numbers. Not like u are a stranger to high horsepower though....
 

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Need larger injectors

You have maxed out the injectors. Your injectors have gone static and can do no more. Assuming a BSFC or .6 and fuel pressure of 74 psi, this adds up to an injector duty cycle in the high 90's. You could make more power with larger injectors. I would increase the injector size and use AFC to pull back fuel on low throttle maps and not quite as much on high throttle maps. This would allow you to fine tune the larger injectors while still using the 850cc VPC EPROM.

Just my opinion.
 

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You're not out of injector

Do you know what chip you have in your VPC? A,B,C or D? SP just did a 76mm single with automatic tranny that made the same Hp as you with 720's.
 
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Re: Need larger injectors

TURBODAWG said:
You have maxed out the injectors. Your injectors have gone static and can do no more. Assuming a BSFC or .6 and fuel pressure of 74 psi, this adds up to an injector duty cycle in the high 90's. You could make more power with larger injectors. I would increase the injector size and use AFC to pull back fuel on low throttle maps and not quite as much on high throttle maps. This would allow you to fine tune the larger injectors while still using the 850cc VPC EPROM.

Just my opinion.
If this is the case, has anyone added extra injectors? I know on high hp turbo bikes, we just mount 4 extra injectors in the airbox. I've also seen a superfueler used on domestic cars for blower applications which adds 3-4 injectors.
 

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Are you measuring EGTs with a GReddy, HKS, Apex, etc. gauge? IF so, the temps may be much higher than you think. On quick pull through a single gear with a high-powered car -- especially on a pull as short as a dyno pull -- those type gauges don't have time to react and indicate the full temperature even though the EGT is actually reaching about the same temp it would reach on a longer pull. I have the Heraeus EGT monitoring system in addition to the GReddy guage. The Heraeus system with its open-element RTD sensors reacts to temperature changes almost instantly. On a quick stab into high boost the GReddy will hardly move while the Heraeus will read 900 C and more. Don't trust those thermocouple type gauges very far.

Steve

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Ok......EGTs were fine, of course - it was just a one gear pull. ......
 

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Re: Need larger injectors

TURBODAWG said:
You have maxed out the injectors. Your injectors have gone static and can do no more. Assuming a BSFC or .6 and fuel pressure of 74 psi, this adds up to an injector duty cycle in the high 90's. You could make more power with larger injectors. I would increase the injector size and use AFC to pull back fuel on low throttle maps and not quite as much on high throttle maps. This would allow you to fine tune the larger injectors while still using the 850cc VPC EPROM.

Just my opinion.
I doubt he is out of injector, Jarrett posted on here that he has made 798 RWHP (no nitrous) on 720cc injectors. 850's should be good for quite a bit more hp. Sorry, I don't have any advise, I just doubt its lack of injector because of some of the examples that we have seen.
 

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I put out 820rwhp with 720 injectors..
 
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Discussion Starter #16
Could you be maxing out the ECU's ability to read more airflow? (850cc / 550cc) * 520 = 803 (of course, this assumes that airflow is proportional to HP, but I'd imagine its not completely linear). That is, assuming it can't read more than 520 rwhp on stock injectors, I really have no idea if that is the case or not. Either way you probably have pretty high duty cycles, but what do I know....
The way I understand it, the ECU only maxes out with the stock mass air's ability to meter air, not in it's lookup tables. The JUN Supra was using the stock ECU, for example.


Congrats on the numbers!!!!! Is this the same setup as the Hayabusa races but without the nitrous?
No, I ran the busa at about 720 rwhp + 70 NOS

You have maxed out the injectors. Your injectors have gone static and can do no more. Assuming a BSFC or .6 and fuel pressure of 74 psi, this adds up to an injector duty cycle in the high 90's. You could make more power with larger injectors. I would increase the injector size and use AFC to pull back fuel on low throttle maps and not quite as much on high throttle maps. This would allow you to fine tune the larger injectors while still using the 850cc VPC EPROM.
I think it's a very good opinion. I calculated the same thing, I just wanted to get everyone's opinion. I am doing what I can with the 720cc prom - last I heard, HKS does not make an 850cc prom.

My pumps are doing their job. Playback verifies that fuel pressure is rising perfectly and maintaining 5 kg/cm^2 when I reach 1.95 kg/cm^2 boost pressure.

As for the max power on 720cc injectors: this isn't a contest. I made 765 rwhp on the 720s for a year. That doesn't make it right! I also read 14:1 A/F by 7500 rpms with the 720s - they were definitely maxing out; same rising A/F curve. Yes, I could just raise the fuel pressure and go for a big number on the dyno, and likely succeed. But that's the wrong thing to do.

Thanks for all the responses, and I am having fun!
 

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Darren,

I don't think HKS makes a 850cc chip for the VPC, but if you're looking for someone to talk to about coming up with a solution, I'd talk to Reg Riemer:

http://www.supras.com/~riemer/sonictech/techtom/

Congrats on the #s BTW...

-m
 

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Marcus Frost said:
Darren,

I don't think HKS makes a 850cc chip for the VPC, but if you're looking for someone to talk to about coming up with a solution, I'd talk to Reg Riemer:

http://www.supras.com/~riemer/sonictech/techtom/

Congrats on the #s BTW...

-m
I have 850's on my car and it runs fine with just some tuning of the GCC. That's with a B chip. You can run a C or D chip to run even fatter upstairs.
 
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White Supra said:

I have 850's on my car and it runs fine with just some tuning of the GCC. That's with a B chip. You can run a C or D chip to run even fatter upstairs.
I have the same setup. I didn't like the C chip, as it was too hard to tune.
 

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Hmmmmm, i'm putting 850's in the car, should i just put the B chip in????
Peter
 
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