No disrespect intended to Alvin, but I find that very hard to believe.

 

Of course.
The problem is that torque will peak and then fall off rapidly (see the dyno chart), and the horsepower falls off very soon thereafter.
Each engine/gearbox combination must be evaluated individually to determine the best shift points.

You cannot deny that revving past the power peak will, eventually be costing power (Past The Power Peak...get it?). The trick is determining just HOW far past the peak is the ideal for your combo...and each gear will probably be different, too.
Hint: it won't be very far past...

Larry
code5coupe

 

I think your engine is just running out of breath.....the heads/cam/intake/exhaust just won't produce power at the higher rpms.

Larry
code5coupe

 

Nathan, your dyno chart looks terrific. Where most street engines are falling off in torque at 4500-5200, yours is still flat, so you are making more power at 6500 than at any other point (I forget the formula for calculating HP, but it is a multiple of the torque and rpm). Nice engine!

 

When an O2 sensor on my right bank ('95 LT1) would break down it went to zero volts. The computer read it as "lean" and reacted by dumping huge amounts of fuel into the right bank. The injector pulse width reading was 30ms on the right bank compared to 16.8 on the left bank; throttle at 73%, according to the AutoXray scanner/data logger. After replacing the faulty O2, I ran another baseline. The pulse width at 95% throttle was 17.6 for one bank and 17.8 for the other and the little LT1 was a happy camper.

My point is that it seems apparent to me that the stock injection system will handle a lot more fuel than the LT1 demands at WOT a lot more than some give it credit for. And, a local speed shop manager concurred that except for a FI application, a 383 would probably run fine on the stock LT1 injectors.

I know enough to get myself in trouble, I admit. But, the fact that the right side of my LT1 was awash in fuel at WOT made it pretty clear there was plenty more before it would ever starve.

What do I know. It just seems there are lots of vendors out there ready to sell bigger injectors. Unless bigger injectors are really needed, it seems to me the computer in closed loop is going to attempt to trim the fuel to "as needed", but integration values are going to be possibly messed up, and idle is not going to be as easy for the computer to control - are thoughts that come to my mind.

Experts not withstanding, I would want to probe the exhaust and monitor it on an analyzer to see mixture is leaning out and/or or look at a dyno readings dipping, manifold temp, or other signs of starvation before changing the injectors (I guess cuz expertise covers a wide range in this hobby). Am I thinkin' wrong here?

P.

 

No you're not thinking wrong. 24# injectors are plenty capable of providing a lot of fuel. If his injectors really are maxed out in the computer and it still runs lean it could be clogged injectors, a weak fuel pump, clogged fuel filter, etc.

It may be none of the above, but I don't see how one LT1 car with heads / headers / hotcam can be fed more than enough fuel by 24# injectors while another car can be starved for fuel unless there is some other car can be starved for it.

 

No problem

one thing you got to remeber is Richards car is a auto with a 3200 stall and gear if I remeber correctly, this skews rwhp numbers making you think that hes not making as much power as he really is.. If I remeber correctly he was putting down over 360


I've still got the dyno runs + afr chart that showes the AFR climbing threw the mid/high 13's at about 6,000RPM. This is after showing richard on my computer the VE and PE tables maxed out proving to both me and him that there was nothign left. not to mention that the PW was over 18ms


For what its worth, I do not sell injectors or any parts for that matter. I have nothing to gain if he buys injectors or not.

If you care to see the AFR chart I'll be more than happy to screen print it and host it somewhere... just let me know, it won't be a problem.

 

It wasn't running out of breath, it was running out of fuel.. As the rising AFR indicates.

 

Your right, its very possible that a weak pump could let us down sooner than expected.. But as far as my experence goes he has those injectors maxed. His car has factory 22lbers which in my experience usually fall short around 350rwhp. A set of 30's would be a nice set up with plenty of room to grow and also they are quite easy to tune in and innexpensive.

 

All factory LT1 injectors were 24's, not 22's.

 

Heres Richard (Ragtop93's) Dyno runs.

They are in dynojet format. If anyone wants them they can email me at Chips@pcmforless.com and I'll send them to you no problem.

This was at a dyno tuning day, Richard was 2nd out of probally 15 so we know the wideband was working as it did great for everyone that day.

As you can see, one run is way fat.. Before I call a fuel system inadaquate i'll do a global change to the fat side.. If the AFR still climbs (specifically at higher rpms due to avaiable time to open vs. time per revolution). This is kinda common practice as we run into Ford lightnings that we tune locally that run out of injector regualarly and its easy to tell what exactly the AFR bump is from..

Back to the point, you can see that even in the globally rich run the car still rises pretty hard at 6k rpm. This indicates to me a inadauate fuel system.. either pump, regulator, injector. Since hes making that type of power threw a 3200 stall, high gear automatic I reccommended (and I still do) to swap up to a set of 30's. 22's are just not cutting it.

 

92, 93 LT1's got 22LBS injectors. They went up to 24's in 94

 

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

 

From a reference source long fogotten...

HP = torque ft-lbs x RPM/5250

P.

 

I have always wondered if the confusion on comparing injectors is the charts in CATS shows 23.8 lbs injectors. But this is at 43psi.
Now ford injectors are rated around 38 psi I believe. So would this not make a 24lb LT1 injector flow about as much as a 22lb ford injector?

It was suggested to me to put a Fuel pressure gage on the car and verify fuel pressure at high rpms. I guess this would eliminate a restriction from the filter or the pump. I will do that and see if it drops.

Assuming it does not drop then at the least I would have to have the injectors cleaned. I would rather replace and then be in line for more hp down the road.


By the way, I have nothing but respect for both Nathan and Alvin as they have both gone way out of their way to help me in the past.

When I made an atempt to try and tune my own car, after my first experience with a custom tuner failed Nathan gave me a lot of good advise and even sent me a bin of his tune (free) which made my car run way better then it did. However there are some differences in our cars.

Anyways I did not have the time or patience to learn to tune my own and that is where Alvin came on the scene. I saw where he was doing a group dyno tune in pa. I contacted him, he sent me a mail order tune to get the car to pa (for free) and then dyno tuned it for $150.00 + $100.00 to the dyno shop for use of the dyno.

Again, they both are two of the most stand up people out there.

 

Forgive my ingorance, but the AFR appears to be going rich (again) from 6000+. Is this an anomoly or??? (I'm just having a difficult time concluding from the dyno graphs (AFR especially) that the engine is starving...at 18ms (pulse width)...when I've seen it as high as 30ms in a faulty O2 condition. I'm loosing the trail here...

BTW, Alvin...Shweeet tune on that *****!!! Congrats!

P.

 

1320dance, Are you tuning your own car or do you have someone to do it for you? The reason I ask is if you are doing your own then you can change your shift points in the programming and get some accurate results at the track. Im not so lucky, I have to play with the govenor or shift manually.

 

The higher the number the leaner the car is.. The lower the number the richer the car is. The car is going lean at 6000+

You'll never see 30ms. Check again. I can post the formula for DC if you want but 30 ms would be over 200% DC at 6000 rpm/.

 

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#

 

Yep, I understand the ratio graph. And, I do see it leaning out - gradually slooping toward the high side. but, like the interesting dip at 4200, the fuel/air ratio graph is tailing down (toward richer) above 6000. I'm curious about that phenominon - all traces seem to follow that general pattern.

As for the 30ms, there is no question the duration (if real) exceeds DC. It was a reading recorded on a data logger when the right bank O2 apparently was shorting out - a zero volts reading at any rate. The engine would break into severe stumbling and missing and the right pipe spewed heavy black smoke - which it would if the right side pulse width was actually 30ms.

Anyway, from a novice point of view, I look at the AFR and hesitate to conclude it is the fault of the injectors, unless 18ms is at the DC threashold for rpms above 6000. And too, I thought I read somewhere that the LT4 possibly uses a slightly bigger injector than the LT1 (if so it would be giving credence to your conclusion).

You're the pro Alvin- I'm just trying to get a "fine tune" on this for my own edification and appreciate your patience!

P.