LIL SS

iTrader: (9)

I am lost here now.. I am trying to figure this whole thing out.

(X*8) / .47=FWHP This formula makes sense to me. This is where I get lost.. I have an M6 so I am figuring 15% drive train loss..

Numbers rounded to the nearest 5hp

FWHP @ 100% Duty, RWHP @ 100% Duty, RWHP @ 80% Duty

28lb injectors = 475, 405, 325
36lb injectors = 615, 520, 415
42lb injectors = 715, 605, 485

Where am I going wrong.. This is how I cam up with my numbers..

(X*8) / .47 = FWHP, FWHP * .85 = RWHP, RWHP * .8 = RWHP @ 80%

I know I am missing something.. Please let me know..


I am scared because of my current setup.. I have done K+N, Direct Flow, BBK, GMAF and have a 100 dry shot on the car. I have not dynoed the car and am guessing at 375 rwhp. but really no idea. If I'm at 375rwhp and my formula is right the injectors would be almost at 100% duty.. Fuel system is completly stock. I haven't hit the N20 since I A-taped and 02's were at .84.. Waiting for my MAFT.

[ November 27, 2001: Message edited by: LIL SS ]

[ November 27, 2001: Message edited by: LIL SS ]</p>

PaiN

[(injector flow rating - lbs/hr) x Duty cycle] / BSFC = FWHP for single injector

Then multiply x number of injectors

Then apply conversion for RWHP

using your numbers for 28lb, duty cycle of 100%, and BSFC of .47

28 x 1.0 / .47 = 59.57

59.57 x 8 (# of injectors) = 476.56 FWHP

rwhp conversion 476.56 x .85 = 405.06 rwhp

--------
same at 80% duty cycle

28 x .8 / .47 = 47.66

47.66 x 8 = 381.28 FWHP

381.28 x .85 = 324.09 RWHP

Your numbers look right to me!

Go to the other thread and read Godspeeds post about using Injectors above an 80% duty cycle

Godspeed

[quote]I am lost here now.. I am trying to figure this whole thing out.
(X*8) / .47=FWHP This formula makes sense to me. This is where I get lost.. I have an M6 so I am figuring 15% drive train loss..

Numbers rounded to the nearest 5hp

FWHP @ 100% Duty, RWHP @ 100% Duty, RWHP @ 80% Duty

28lb injectors = 475, 405, 325
36lb injectors = 615, 520, 415
42lb injectors = 715, 605, 485

Where am I going wrong.. This is how I cam up with my numbers..

(X*8) / .47 = FWHP, FWHP * .85 = RWHP, RWHP * .8 = RWHP @ 80%

I know I am missing something.. Please let me know..


I am scared because of my current setup.. I have done K+N, Direct Flow, BBK, GMAF and have a 100 dry shot on the car. I have not dynoed the car and am guessing at 375 rwhp. but really no idea. If I'm at 375rwhp and my formula is right the injectors would be almost at 100% duty.. Fuel system is completly stock. I haven't hit the N20 since I A-taped and 02's were at .84.. Waiting for my MAFT.
<hr></blockquote>

1. In our RPM range M6 drive train loss is a fixed 45RWHP, not a 15% percentage.

2. From the bolt-ons you have listed it sounds like you're closer to the 320RWHP mark, unless you have a cam - not 375RWHP.

3. The 28# injectors can support 405RWHP (dynojet manual) at 100% duty cycle and maintain safe air/fuel ratios. My guess is that you are at 320RWHP and a "100 shot" would take you to about 415RWHP. As long as you used the juice in short bursts you will be fine. If you are worried splash in a small amount of 104 octane gas when you want to use the nitrous.

But no, the sky is not falling. People including myself have been safely using 100 shots of nitrous on stock LS1's and their fuel systems for several years. By being safe, spraying from 3k-6k, never for more than 10-15 seconds at a time, and never at high speed or high load conditions (5th gear.)

4. Personally I would drop the GMAF especially when spraying dry and stick with a stock MAF. I had problems with getting one to work on my car, but I think they do have a "dry nitrous calibrated" version now.

5. The LS1 has a BSFC of 0.50, not 0.47 unless you specifically pulled your engine and measured it's flywheel horspepower on an engine dyno.

-Jeremy

[ November 27, 2001: Message edited by: Godspeed ]</p>

Colonel

What kind of fuel/air ratio would 500 RWHP with a M6 and 28.6 lb injectors be?

What would it be with 480 RWHP with an A4 and 26.4 lb injectors?

I ask because I know this has been done but it obviously is EXTREMELY lean according to calcutions.

If 405 RWHP is %100 duty cycle, should 500 RWHP even be possible?

One more point, shouldn't we be taking RPM into consideration? I mean, an injector does have %50 more time to get it's work done at 6000 RPM than at 9000 RPM, right?

If so, what RPM is 405 RWHP %100 at? If it's at 6000, what would the max be at 7500? 5500?

[ November 27, 2001: Message edited by: Colonel ]</p>

LIL SS

iTrader: (9)

[quote]Originally posted by Godspeed:
<strong>

1. In our RPM range M6 drive train loss is a fixed 45RWHP, not a 15% percentage.

2. From the bolt-ons you have listed it sounds like you're closer to the 320RWHP mark, unless you have a cam - not 375RWHP.

3. The 28# injectors can support 405RWHP (dynojet manual) at 100% duty cycle and maintain safe air/fuel ratios. My guess is that you are at 320RWHP and a "100 shot" would take you to about 415RWHP. As long as you used the juice in short bursts you will be fine. If you are worried splash in a small amount of 104 octane gas when you want to use the nitrous.

But no, the sky is not falling. People including myself have been safely using 100 shots of nitrous on stock LS1's and their fuel systems for several years. By being safe, spraying from 3k-6k, never for more than 10-15 seconds at a time, and never at high speed or high load conditions (5th gear.)

4. Personally I would drop the GMAF especially when spraying dry and stick with a stock MAF. I had problems with getting one to work on my car, but I think they do have a "dry nitrous calibrated" version now.

5. The LS1 has a BSFC of 0.50, not 0.47 unless you specifically pulled your engine and measured it's flywheel horspepower on an engine dyno.

-Jeremy

[ November 27, 2001: Message edited by: Godspeed ]</strong><hr></blockquote>


Jeremy,
Thank for the info.. I figured the 375 to be on the bottle. I didn't think as high as 415rwhp.. I also didn't know about the 45hp loss instead of 15%..

Just for your knowledge the GMAF for dry shots is reprogramed to be 5% or so richer than the one the sell for non-N20 apps. I spoke to Granatelli when a SES light was coming on when I did it. They advised because of the other intake mods I did the MAF needed to be a little richer. This brings up another question.

Granatelli mention the MAF could only be reprogramed to allow about 15% increase in A/F like the MAFT does, after that bigger injectors are needed. So with them setting me 5% richer when I put my MAFT on will I be really only be able to adjust say 10% instead of 15%?

Thanks for the info again..

Terry Burger

iTrader: (4)

[quote]
1. In our RPM range M6 drive train loss is a fixed 45RWHP, not a 15% percentage.
<hr></blockquote>

This is another point I think Dave@Incon is wrong about. It's really closer to 20rwhp+6%*RWHP in my opinion.

LIL SS

iTrader: (9)

20hp?? Is GM really getting that efficient? It does not see possible to me. But hey, I don't know everything. That is why I am here asking things..

Colonel

He said 20 HP PLUS %6.

LIL SS

iTrader: (9)

Colenel,
Thanks, I missed the + sign..

RPM WS6

iTrader: (3)

This is a good post. I haven’t done a lot of investigation into injectors yet as I feel that with my planned setup for next year I’ll only be in the 340/350 RWHP range (A4) and I don’t think I even need to worry about injectors yet.

But I have a friend with a 5.0 stang (I know it’s a totally different motor) who always swears by increasing injector size even on a stock na motor. When I told him I was going to try and support about 400 FWHP on my stock 26lb injectors he nearly freaked! I know he was thinking in 5.0 terms, but he is very knowable and I trust his opinion. So my question is, is he totally off base when it comes to LS1s, or does he have a point? He recommended somewhere around 36lb for my setup “at least”. I think that’s really going over board. My fuel trims are no where near maxed out now and I’m at about 310 RWHP now, so with adding only about 30 to 40 more RWHP, is this something I should even consider?

LIL SS

iTrader: (9)

Another question as well.. Lets say I only have 325 RWHP. Could you have too much injector? Lets say I put 42lb injectors in. Could I have a problem?

pedaltothemetal

[quote]Originally posted by LIL SS:
<strong>Another question as well.. Lets say I only have 325 RWHP. Could you have too much injector? Lets say I put 42lb injectors in. Could I have a problem?</strong><hr></blockquote>

Please don't put 42LB injectors in cause you don't need it. If you do you will soon know you have made a terrible mistake and have to reinstall your stock ones and wasted $400.

Leo

Godspeed

[quote]What kind of fuel/air ratio would 500 RWHP with a M6 and 28.6 lb injectors be?<hr></blockquote>

It depends on what type of engine and how the power is achieved, along with the tuning and RPM. Are you talking about a 422 making that much power NA? Or a stock LS1 spraying a dry shot? The best thing to do of course it to put the car on a dyno with widebands so you will know for sure, but I would estimate the AFR to be in the mid 13:1 range for the scenario described past 5500RPM.

[quote]What would it be with 480 RWHP with an A4 and 26.4 lb injectors?<hr></blockquote>

Is this the setup you are running with your 422? Again my response from above applies.

[quote]I ask because I know this has been done but it obviously is EXTREMELY lean according to calcutions. <hr></blockquote>

Agreed, this is the point I made in one of my last replies in the other injector thread. The industry standard fuel calculations do indicate that at the power levels we achieve we should be running extremely lean, yet you myself and many others have proved for years that we can get away with this. I do believe the formulas to be fairly accurate (unless the LS1 has a significantly lower BSFC than 0.50 which I doubt.) I give the LS1 fuel systems and PCM credit for keeping up with the demand for very small periods of time. Perhaps the stock injectors deliver more fuel than we thought - that's why I had mine flowed to verify this, but they were dead on to there rating.

The only point I'm trying to make is that these formulas are good for approximating what size injectors you should go with, but before making big power you should monitor the car and see what it is actually doing, instead of assuming the fuel system is keeping up. I have seen quite a few cars turn big power numbers, and high trap speeds on stock fuel systems. I still contend that these extremely lean conditions are only occuring for very brief periods of time as RPM increases and that's why you are able to get away with it. The bottom line is, if it works, it works, you can't argue with that, regardless of what calculations indicate.

[quote]If 405 RWHP is %100 duty cycle, should 500 RWHP even be possible?<hr></blockquote>

It is possible because I have done it with a bolt-on 1999 LS1 on dry nitrous and 104 octane race gas. However on 93 octane the fuel system was inadequate and the motor detonated and broke pistons. Lesson learned the hard way.

[quote]One more point, shouldn't we be taking RPM into consideration? I mean, an injector does have %50 more time to get it's work done at 6000 RPM than at 9000 RPM, right?<hr></blockquote>

Exactly RPM is very important and as I'm sure you are aware this is where calculating injector pulse width comes into play. At 6000RPM you only have 10ms to deliver fuel. If the PCM is calling for an injector pulse width of 20ms then all the fuel isn't going to make it in. Or is it? Will it puddle? A larger injector will deliver more fuel in a smaller pulse width allowing increased delivery in the smaller time windows at higher RPM. This is how Steve Cole builds his fuel maps - by calculating how much fuel he needs to deliver in an RPM vs. pulse width table.

To accomplish these calculations you need to dyno your car with widebands and use autotap/tech2 to monitor things. After the dyno build a table from the logged data of RPM vs. A/F and RPM vs. injector pulse width. Compare the data and then make power enrichment changes based on that. Not exactly a pure science, and not exactly trial and error either - fine tuning.

[quote]If so, what RPM is 405 RWHP %100 at? If it's at 6000, what would the max be at 7500? 5500?
<hr></blockquote>

The 405RWHP number derived from the formula does not take into account RPM or indicate what AFR should be achieved as far as I am aware. It's because of this that these figures are generic, not LS1 specific, and are mainly just based on the BSFC. See my prior statements for using these as a guideline then checking to see what your car or the LS1 is actually doing.

Besides these vary good points you've made regarding RPM another important factor to consider is the spray pattern of the injector. The GM injectors have a long and narrow spray pattern and this is one reason that Steve Cole recommends them over the SVO injectors for use with the LS1. If an injector has a short wide spray pattern the fuel may not quite be making it where you think it is.

[ November 28, 2001: Message edited by: Godspeed ]</p>

Godspeed

[quote]Another question as well.. Lets say I only have 325 RWHP. Could you have too much injector? Lets say I put 42lb injectors in. Could I have a problem? <hr></blockquote>

Agreed I have seen what 42# injectors do with a stock PCM. They simply put out to much fuel and it won't even idle correctly. It stumbles, misfires, and wll foul plugs. I don't think a MAFT can compensate for this much on an injector change either, the PCM would have to be programmed for them. When mine was programmed for the 42's, it was a night and day difference, and it idled nice and smoothly afterwards.

LIL SS

iTrader: (9)

I think I am going to leave the car alone for the most part right now. Planning for near future.. Put a MAFT on it and leave it for now. But I think I am going to start buying the parts..

My plan in the next year to year an a half is heads, cam, headers, full exhaust.. So I'm thinking the 42 lbers is the dirrection I am going to go. Is it possible that LS1 edit will alow me to do the tunning I need when it is out?

Trevor @ Texas Speed & Perf.

iTrader: (3)

[quote]Originally posted by RPM WS6:
<strong>He recommended somewhere around 36lb for my setup “at least”. I think that’s really going over board. My fuel trims are no where near maxed out now and I’m at about 310 RWHP now, so with adding only about 30 to 40 more RWHP, is this something I should even consider?</strong><hr></blockquote>
Did your friend take into the consideration the higher fuel pressure that the LS1 sees? If I remember correctly, I was told that the FMS 30 lb/hr injectors are actually 36 lb/hr injectors w/ our fuel pressure. With that being said, I'd HATE to see what a set of 42 lb/hr injectors are with our 58-60 psi of FP!

RPM WS6

iTrader: (3)

[quote]Originally posted by Trevor D:
<strong>
Did your friend take into the consideration the higher fuel pressure that the LS1 sees? </strong><hr></blockquote>

Probably not! The last F-body he owned was an early third gen with a 4bbl.

So you would say the stock ’00 units would be good enough for ~350 RWHP (A4) totally NA revving to no more than 6200 to 6300 rpm?

Godspeed

LIL SS:

[quote]I think I am going to leave the car alone for the most part right now. Planning for near future.. Put a MAFT on it and leave it for now. But I think I am going to start buying the parts..
My plan in the next year to year an a half is heads, cam, headers, full exhaust.. So I'm thinking the 42 lbers is the dirrection I am going to go. Is it possible that LS1 edit will alow me to do the tunning I need when it is out? <hr></blockquote>

I agree your existing injectors should be fine for that setup and using the MAFT to dial it in should be fine. LS1 Edit when it is out will allow you to change the injector size.

Trevor D:

[quote]Did your friend take into the consideration the higher fuel pressure that the LS1 sees? If I remember correctly, I was told that the FMS 30 lb/hr injectors are actually 36 lb/hr injectors w/ our fuel pressure. With that being said, I'd HATE to see what a set of 42 lb/hr injectors are with our 58-60 psi of FP! <hr></blockquote>

At LS1 fuel psi SVO 42's flow about 49lbs/hr.

sqrt(new psi/old psi) x old flow rate = new flow rate

RPM WS6

[quote]So you would say the stock ’00 units would be good enough for ~350 RWHP (A4) totally NA revving to no more than 6200 to 6300 rpm? <hr></blockquote>

BSFC=0.5; Injector Size=26.4#; Injector Duty=100%

(inj. size) (inj. duty) / (BSFC) * (# of inj.) = HP

(26.4 x 1.0) / (0.50) x 8 = 422.4

That would come out to approx ~420 flywheel HP. With 18% A4 drivetrain loss that would be approx. ~345RWHP.

So according to those calculations past 345RWHP in a 2000 A4 (with 18% drivetrain loss) you would start to go lean.

Take it for what it's worth, I would just use autotap or a good dyno to see how your car is doing.

-Jeremy

[ November 28, 2001: Message edited by: Godspeed ]</p>

RPM WS6

iTrader: (3)

Godspeed...Thanks for your insight in my case. I appreicate your comments. I'll just keep an eye on it with A-tap and see what happens.

Terry Burger

iTrader: (4)

The bottom line is stock fuel injectors are fine for almost all of the 346ci heads/cam setups, and 36#ers are fine for everything else.