Hotcam
Drifting
Joined: May 2003
Posts: 1,730
Likes: 1
From: Charlotte NC
St. Jude Donor '05
Originally Posted by Nathan Plemons
Alright so you can't argue with the part numbers. My car actually has a set of stock injectors out of a '95 so maybe that is the difference.
Unlike some people, I'll admit when I'm wrong
What is interesting though is that the injector constant on a stock '92 is programmed closer to 24# than 22#
Unlike some people, I'll admit when I'm wrong
What is interesting though is that the injector constant on a stock '92 is programmed closer to 24# than 22#
Its also got 10:1 programmed into the PE table but they really do about 12:1.. I think they set that stuff about right.. then tune on it from there. The later model cars has 24.8 or something like that while the 93's have 24.1 Niether of which makes any sence.
Drifting
Joined: May 2003
Posts: 1,730
Likes: 1
From: Charlotte NC
St. Jude Donor '05
The dip at 4200 RPM is when we where able to start the dyno run. Cars with higher stalls have a hard time on the dyno wihtout downshifting.. You got to wait until later to start the run.. Then when you do start the run you want to see it dip down a good bit.. This makes the car feel responsive on teh street and keeps it from choking.. At car that sat at 13.0 the entire time is unrealistic and wouldn't feel right when you slammed the throttle down.
The dip after 6000 down to rich is from when we just let off the gas. You can see HP/TQ dropping off hard at the same time. Thats the end of the run. If we would carry it on, the HP would have arc ed over easy as the AFR climbed higher and higher.
The thing is about 30 ms is.. you don't have 30 ms per crank cycle at 6000 RPM.. You only have about 18ms.. SO if your fireing that entire crank cycle that means you are at 100% DC which is just (Ontime/per time)
The dip after 6000 down to rich is from when we just let off the gas. You can see HP/TQ dropping off hard at the same time. Thats the end of the run. If we would carry it on, the HP would have arc ed over easy as the AFR climbed higher and higher.
The thing is about 30 ms is.. you don't have 30 ms per crank cycle at 6000 RPM.. You only have about 18ms.. SO if your fireing that entire crank cycle that means you are at 100% DC which is just (Ontime/per time)
Drifting
Joined: May 2003
Posts: 1,730
Likes: 1
From: Charlotte NC
St. Jude Donor '05
Originally Posted by Nathan Plemons
Well for what its worth then a set of stock injectors out of a later LT1 will supply the fuel that you need. As will a set of SVO 24's. I just like the GM injectors better for some reason.
I would still like to see him use a 30.. They are cake to tune in and on top of that he sprays.. I would rather him get away from high DC's with spray. A injector locking up would be disasterous
Drifting
Joined: May 2003
Posts: 1,730
Likes: 1
From: Charlotte NC
St. Jude Donor '05
Originally Posted by Nathan Plemons
LT4's had what 26# injectors?
LS1's are supposed to be 28's but yet at a different fuel pressure as well correct?
LS1's are supposed to be 28's but yet at a different fuel pressure as well correct?
You have to be careful with LS1 injectors as almost every year flows differeently. Most of them flow about 25#/hr at 43.5. There was one year of them that flows nearly 28.. I think the 00's.. The LS6 injectors are also larger.
Race Director
Joined: May 2001
Posts: 14,165
Likes: 9
Fair enough if you plan on spraying it. As it is though I would much rather use a wet kit and not have to rely on the injectors.
A friend of mine has an LT1 with the NOS throttle body dry kit. The car was really running for crap, when he pulled the heads off of it he could see it was very obvious that the nitrous to each cylinder was not evenly distributed. He had one spark plug that had the ground strap blown clean off of it, while others looked as if they had been running rich, etc.
He put it all back together with new heads. He's going to put nitrous back on it but it is going to be a direct port kit instead. This will ensure a better nitrous distribution and won't rely on the 24# injectors with jacked fuel pressure to supply the fuel. It seems like the much more reliable option.
A friend of mine has an LT1 with the NOS throttle body dry kit. The car was really running for crap, when he pulled the heads off of it he could see it was very obvious that the nitrous to each cylinder was not evenly distributed. He had one spark plug that had the ground strap blown clean off of it, while others looked as if they had been running rich, etc.
He put it all back together with new heads. He's going to put nitrous back on it but it is going to be a direct port kit instead. This will ensure a better nitrous distribution and won't rely on the 24# injectors with jacked fuel pressure to supply the fuel. It seems like the much more reliable option.
Drifting
Joined: May 2003
Posts: 1,730
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From: Charlotte NC
St. Jude Donor '05
Alot of time you see this with guys who put the nitrous too close up on the intake tract.. Did you say he was using one of teh NOS throttle bodys? I have 0 experence with them..
instead of nitrous distribution maybe it was fuel distribution problems. high pressures and high injector duty cycles are a no-no.
instead of nitrous distribution maybe it was fuel distribution problems. high pressures and high injector duty cycles are a no-no.
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Melting Slicks
Joined: May 2002
Posts: 2,670
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From: Severna Park MD
Originally Posted by Nathan Plemons
Well for what its worth then a set of stock injectors out of a later LT1 will supply the fuel that you need. As will a set of SVO 24's. I just like the GM injectors better for some reason.
The later 24 lb injectors from 94 on do supply more than enough fuel for a Hotcam car. But if a tuner only knows the 30 lb injectors really well then a mail-order tweak might not be doable with the later stock 24 lb injectors. You won't find many 92-93 cars using the later injectors like Nathan is doing.
Last edited by FELNGR8; Aug 11, 2005 at 11:01 AM.
Race Director
Joined: May 2001
Posts: 14,165
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Originally Posted by Alvin
Alot of time you see this with guys who put the nitrous too close up on the intake tract.. Did you say he was using one of teh NOS throttle bodys? I have 0 experence with them..
instead of nitrous distribution maybe it was fuel distribution problems. high pressures and high injector duty cycles are a no-no.
instead of nitrous distribution maybe it was fuel distribution problems. high pressures and high injector duty cycles are a no-no.
Drifting
Joined: May 2003
Posts: 1,730
Likes: 1
From: Charlotte NC
St. Jude Donor '05
Originally Posted by FELNGR8
My 94 car has the identical valve train components you find in Richard's car, but it's a 6 speed. The 6 speed just lets me get a solid pull from 2200 rpm to 6200 with no unknown torque draw from TC and such. My current tune goes progressively richer from 13.0 at 2900 all the way to 12.2 at 5900 rpm, then slightly tends back toward lean to end at 12.5 at 6200.
The later 24 lb injectors from 94 on do supply more than enough fuel for a Hotcam car. But if a tuner only knows the 30 lb injectors really well then a mail-order tweak might not be doable with the later stock 24 lb injectors. You won't find many 92-93 cars using the later injectors like Nathan is doing.
The later 24 lb injectors from 94 on do supply more than enough fuel for a Hotcam car. But if a tuner only knows the 30 lb injectors really well then a mail-order tweak might not be doable with the later stock 24 lb injectors. You won't find many 92-93 cars using the later injectors like Nathan is doing.
Its not a matter of knowing how to get it to work.. Its a matter of something thats just a hair bigger and something that is a good bit bigger for the same price. He he puts 24's in he will likely still be over 90% DC. If he has 30's than he will fall nicely in the 80% range..so hes safer and has room for the next mod.. for the same $$
Drifting
Joined: May 2003
Posts: 1,730
Likes: 1
From: Charlotte NC
St. Jude Donor '05
Originally Posted by Nathan Plemons
Well such as it was the guys from Holley actually provided and set up the NOS system so I would really hope it was set up to their specs.
I'll bet its just a fuel distribution problem. Dry kits really lay on the PSI.. thats not so great for those injectors.
Race Director
Joined: May 2001
Posts: 14,165
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Dunno man, he's got a big nasty in tank fuel pump, Holley injectors, etc. It ran fine on nitrous, it just had the small problem of blowing out spark plugs. Regardless a direct port wet kit is the safest most reliable
way to do it.
way to do it.
Burning Brakes
Joined: Nov 2001
Posts: 920
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From: Cherry Hill NJ
Originally Posted by Alvin
Nathon, if you would like I have a injector partnumber chart/lookup it has probally 1000 different part numbers... every 92-93 LT1 i've seen has had the '7325 Rodchestors (or equivelent).. they are rated at 209 cc.. The 94+'s went to a 219 cc.
Edit
Here it is..
http://www.powerpage.dk/produkter/pic/injectors.pdf
Edit
Here it is..
http://www.powerpage.dk/produkter/pic/injectors.pdf
Le Mans Master
Joined: Apr 2000
Posts: 5,713
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From: Manassas VA
I may be wrong in my way of thinking on injector sizing but here goes. I believe the injector size is more based on hp then CID. That being said GM used a 24lb injector in a 300 hp LT1. Well for some reason they put 28lb injectors in a 330 hp LT4. Now I know that their engineers could have made the 24's work but for some reason they went to 28's I think it has to do with safe limits on the injectors. That being said it is not unreasonable to put 30lb injectors, (which may be 32 or 33 if rated at the same pressure GM uses) in a car making 362rwhp. If I am wrong, tell me, but be nice 
Le Mans Master
Joined: Feb 1999
Posts: 9,933
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From: South Carolina
St. Jude Donor '03 & '05
Beehive springs, which fit in stock cups and a better than factory timing chain(IE Extreme duty chain), and you can hit 6500 rpm all day. With the Hot Cam you can do 6200 rpm , as I think it starts to fall off power wise around there anyways.