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We just got back from a day with Russ Collins of RC Engineering with very informative testing on the 2002 Z06 injectors.

They are Bosch Injectors which flow 255.0 cc/min at 43 psi or 24.29/lbs/hr. each. They were actually fairly well balanced for off the shelf smog type injectors. If my memory serves me correctly, they are the same size as the 2000 LS1 injectors we tested this year. If you use the calculations for max HP at 55 psi (static fuel pressure) at .46BFSC (Brake Specific Fuel Consumption), and 80% duty cycle this size is good to roughly 390 Crank HP. Russ says that the goal shoud be .50 BSFC at static pressure and around 80% duty cycle.

These stock injectorscan make the 405 HP claimed by GM, but the duty cycle will be around 85% which is acceptable limits.

Here's the problem. Add an intake (any intake system) and you will increase airflow from 12% to 16% depending on the intake configuration. If you try to reach the same a/f parameters with these stock injectors, the duty cycle goes up until out of range and a lean WOT with pinging is the result.

Russ looked at the AutoTap air fuel mixture recorded recently on our 02 and said they are dead nuts on, for max performance on the street or drags. We were using the 310cc Injectors we sell with out T-1 kit. He recommended that size as a minimum, and larger 370cc for Z06s with heads and cams.

Katech Engines (C5R engine builders) sell a LS1 to Z06 conversion kit with heads and cam and recommend 36 lb/hr injectors with their kit. Russ recently met with the owner of Katech to share R&D information.

Our plugs were responsible for the apparent loss of 4 HP on our recent dyno testing. They worked in our LS1 but not in the Z06.

Bottom line: The stock injectors are capable of maybe 480 HP, but would be maxed out at 100% duty cycle with no headroom at that HP. If you watch your dyno with an AutoTap onboard, the a/f mixture will end up above 13:1 with injectors running at max duty.

310 cc RC Injectors are good to 475 HP at 80% duty cycle and 530 HP at 90% duty cycle. At the 85% duty of the Z06 injectors they will be at 493 HP. Much better headroom for those who are on a mod quest.

Check out this link to figure out your injector sizing for different setups.

http://www.corvettec5.com/cgi-bin/S...echnical[1].htm?L+scstore+tbsd4207+1000857877

For the above examples, we are using .46 BSFC as determined by our stock dyno testing.

Jim Hall
Halltech

* We also stock the RC 270 cc/min injectors which have 6% more flow rating than stock. The 310cc/min injectors have 22% more flow. The RC 270 cc/min would be closer to stock and work pretty well will just an intake mod. If you plan on going further, i.e. headers, 1.8 rockers and exhaust mods, the RC 310cc/min static flow rate injectors would be best. Heads, cam and other major mods- RC 370cc/min injectors would be the ticket.

Have fun with the calculator.
 

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Jim thanks for the info, I talked with you on the phone last week about the plugs. Thanks again for the honest good info. If my plugs are white as caspers ass, would a larger fuel injector help or would the computer just tune out more fuel?



Note: I talked to Jim about buying some plugs from him and he told me not to waist my money. great guy. thanks again

:cheers:
 
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BADASSZ06 said:
Jim thanks for the info, I talked with you on the phone last week about the plugs. Thanks again for the honest good info. If my plugs are white as caspers ass, would a larger fuel injector help or would the computer just tune out more fuel?



Note: I talked to Jim about buying some plugs from him and he told me not to waist my money. great guy. thanks again

:cheers:
Actually, the injectors do not add fuel to the closed loop trims. They are fully blueprinted and balanced within 2 cc/min which allows much cleaner trimming of both banks. The additional available fuel delivery is not used until its needed. When the MAF "senses" more airflow, say from a new intake, the O2 sensors automatically adjust the short term fuel trims in each fuel cell back to 14.6:1. It takes a few driving cycles to adapt the PCM.

WOT, however, being an Open Loop (no O2 feedback) takes it's cue from the factory air fuel ratio and adds or deletes some fuel at the beginning of the cycle. It does this based on the very last fuel cell your TPS was in as you entered WOT (cell 22). In this way the computer can provide some additional fuel trimming in WOT.

Programmers like Steve Cole and others try to set the Long Term Trims close to zero, in order to provide the best a/f ratio for your particular ride. Each engine is different, every day is different, so the computer must be a dynamic learning machine to provide a proper a/f ratio for all conditions and environments.

This is another reason why dyno numbers vary all the time. Even the throttle position you are in before your dyno WOT pull affects the run to a degree.

The stock injectors work just fine for stock, and will work for some mods, but they are definately at the end of the road beyond intakes.

Our 310 cc/min injectors are rated at 43 psi but the 55 or so available puts them even higher. Their static rating is 29.6 lbs/min. and our plug chops are pure white porcelin.

Now we know how GM managed to delete the pups and bring the 2002 another 20 HP. They did it will some awesome air delivery, over 25% more airflow at the MAF.

We now have the 2002 Z06 MAF sensors available for $179.00 if anyone wants them. They have a different part number to the honeycomb laminar screened LS1 version, but testing will reveal if there is a real difference other than the screen removal. The difference in price would suggest that.

We are offering the TRIC T-1 SideWinder Intake pre-assembled with the new 2002 Z06 MAF installed for $778.00. Call on this.

Hope this information helps. I'll continue to post our findings as they develop.

Jim Hall
 

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Jim, your post is very educational. Thank you!! :cool: I may call you this week, I have some mod questions for you. :) I'm not sure which direction I need to go.
 
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Discussion Starter #8
Re: which plugs are you talking about?

vortech said:
what plugs brand and part # caused this loss of hp-i was going to replace my stock ones with ngk tr55's gapped at .050 thou. :-?
BTW: Excellent 1/4 mile numbers so far!

Not those. They were the Champion Copper RS12YC plugs. The factory gap is about .035", and the Z06 needs .065" to .070".

These plugs can be regapped, but the electrode is not square with the tip, causing the spark to ignite at about .035", creating a smaller than needed kernel. GM's website indicates .065" minimum gap if my memory serves me. (and it doesn't very often)

I have not dynoed the NGKs, but I've heard good reports about the Berus. We'll check those out next.

Jim
 

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Jim, I was under the impression that the 2001 corvettes (maybe just the Z) and cadillacs for a few years now did closed-loop WOT.

I've heard it from several different sources, so I figured it was most likely true.

Have you heard anything like this?
 
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OL2

Fuel cell 22, which corresponds with WOT is definately an open loop setting. I would be happy to share our AutoTap information with anyone who has the software.

It can be downloaded free on www.AutoTap.com

During the AutoTap logs the moment you go into WOT the next frame shows a minor correction of a/f coming from the last cell you are in JUST before WOT. It is my understanding that there is a minor adjustment in the WOT from that data.

All O2 input is off (Open Loop) when in cell 22. Watching our a/f ratio with the injectors, starts at around 12.6:1 and dynamically changes thoughout the rpm range until at 6600 rpm it is 12.1:1.

I would like to see between 12.6 to 12.8:1 for max hp, but under the load of the dyno, spark knock is a dyno report killer on this car. The fatter mixture cuts power a tad, but nothing is lost to spark knock.

Our T-1 package is onboard now, with the T-1 SideWinder.

We will run 11.90s. Bold talk? Just wait and see.

Jim Hall
 
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