I just got back from the Dyno and Track. I am ****ed.

[UB2 SLOW]

Okay, I got the car running good before I went to the Dyno. Thanks Vettelt193. You are the man;worship But here is the problem. I dynoed out at 302hp at 6000 and 300 tq at 4500. My understanding was with the mods that I have I should have about 350-360hp. The best I could muster at the track was a 13.021 at 105.89. Before the mods I dynoed out at 255 hp at 5600 and 281 tq at 4400 and ran a 13.484. I am really disgusted right now. Can anyone help? On what would have been my best run of the night, I had a react of .525 and a 60ft time of 1.886. I ended up running a 13.214 after my torque convertor locked up in second gear at around 5400 rpm.

My mods are LT4 hotcam, LT4 heads, LT4 intake, 58mm Throttle Body, Hooker Shorty Headers, 1.6 rocker rolles, Stage II port & polish, Underdrive pulley, 8mm taylor wires, Ed Wright Programming, 30lb injectors, adjustable Fuel pressure regulator, ended up being set at 44, yank 2800 TC, 3.73 gears. The Cam, Heads, Intake, throttle body, 1.6 rr, 30lb injectors and programming were all recommendations by Pace Performance based on a kit that they sell. The kit is similar to LPE, MTI and TPIS.

 

[Trance_LT4]

I think you'd be better off with a 52mm TB personally. My LT4 dynoed identical to yours when my mod list only included the flowmaster exhaust and MSD6a. Our times are also pretty close, at that time I ran a best of 12.9 @ 109. So, with your LT4 conversion plus some, you SHOULD be above that in HP/TQ.

28lb injectors are good to 430hp, but I wouldn't see where 30 hurts

Shorty headers = useless IMO. They aren't any better than manifolds.

Here is the old "if it were me" line:

I'd put a 52mm TB on there, restore the fuel pressure to LT4 stock 41psi (since LT1/LT4s are so sensitive to pressure changes), stock 28lb LT4 injectors (with corvette part numbers--- you wanna get the impedence right) and have a look at that programming.....a hosed up program can make all the difference.

Once you see a gain, bump the pressure back up and try the 30 pounders again. The 58mm TB will come back into play when you're above 420hp or so

 

[BigRed]

Just sounds like your "bogging" the motor with to much air. Ive read alot of threads regarding the 58mm throttle body (Including my own) And it seems the L98 Plenum ported or not isn't large enough to house the air provided by the 58mm TB.

I agree put the 52mm back on or increase the size of the plenum via Lingenfelter/Accel/TPiS Large runners/or Miniram.

 

[Trance_LT4]

This isn't an L98, so there is no plenum to swap/increase. However, the statement still holds true, 58 is too big for a naturally aspirated 350 with generally mild modifications.

Thinking about this a little further... the bottom end of your engine is just a pump, and the heads are really where the good stuff happens.
If the small fixes like 52 or stock throttle body,stock injectors ect...doesn't fix the problem, you might look at things from a diff perspective. Maybe the stage 2 port job isn't meshing with your stock displacement...........does "383 stroker" sound appealing? Your setup seems RIPE for larger displacement.

 

[BigRed]

Ahh damn my bad LT series

(Ima gonna just walk away inta dat sunset with my tail between ma legs)

 

[WhalePirot]

programming?

Sorry to hear of your WOE.

I spent mega-bucks for my mechanics time, to get my 406 to run, despite two previous 'custom' chips. It now screams to 6200+ with a 52mm BBK. It only shuts down above 6500 due to a safety in the computer, as it wants to keep revving; badly! It also idles nicely (obvious, though, to the most casual observer, that the cam is NOT stock) at 875-900, and just passed Calif. emission with flying colors. I can take Vipers and ZR-1s, no prob. Mustangs? Ricers? U think I'll bother wasting my fuel? :booty

I was not charged for all the time these guys spent on my chip, but I'd not be surprised to find that I have over $1k in this chip. The engine was under $5k, itself. But, do I have results! And, bigger is not better. Optimal is best.

I built the 'same' engine as a friend. 'His' chip would not run my car worth a damn! Go figure. Now tell me that you can call in your engine specs and get it right? Tell me, that w/o a painstaking process WITH YOUR CAR, any chip wizard will get it right! Nope. I USED to think so.

Folks, these cars are computer controlled. Computers are STUPID. The can do wonderful things, but the days of fiddling with the idle speed, jets and mixture; then accepting lousy driveability, but great racing, are gone, unless you go back to a carb. The ECM needs to know almost exactly what to do, as it has a limited range of adjustment.

He also claims my MSD box is a waste of money unless running above 6500rpm. Below that, HEI works fine. The ignition system delivers only the amount of voltage needed to fire the plug. If it takes 12kv to fire the plug, why is capability to produce 100kv better than 50kv?

There are two schools of thought on fuel pressure. Some like to run smaller injectors at higher pressure, claiming better spray. Others size the injectors for HP, (proper, I think) and run stock fuel pressure. The ECM wll fine tune for proper burn, within limits. Use ONE expert; balance your upgrade parts and let a GREAT programmer make it run.

The point is, don't throw all your money at big name parts, without aq goal and an expertly guided paln. You'll need a big wad to get some guy to drive or dyno your car and customize your chip. Non dyno method takes a lot of time (to explore all the fuel tables, etc.). He has to see what the computer is doing and if it CAN do its job given its limitations. This takes TIME and personal attention. Anything else is luck or less than optimal.

Trust me. BEEN there DONE that.



1984 Z-51 Corvette (white/carmine)
406 cid four bolt, forged crank;
11:1 with aluminum Dart Pro-1 heads
FMS injectors- 30pph @45 psi; BBK 52mm
Lingenfelter Superram plenum, runners & base
Comp hydr. roller- 230 intake; 236 exh @.050
TPIS long tubes>3" thru new, stock '84 Vette cat> Flowmasters

- 315/35x17" on black Epsilons
- Bilsteins revalved to 'Challenge' specs
- Heim jointed 3.73:1 rear; poly everywhere
- lowered 3/4"
- strengthened super T-10 and Nash O/D
- Optima battery, behind passenger
- 'export' taillights (ambers, outside, flash only)
- new leather/cushions/wood dash/wheel

 

[UB2 SLOW]

Do you know of anyone in NC that can tune it for me? The only way I can tune it is by changing the fuel pressure. I really dont have the cash for a 383. I started thinking about it right after I got back from the track. It would take about a year before I could attempt something like that.

 

[Vettelt193]

Are you talking RWHP? if so, you aren't doing all that bad... with a 20% loss for the automatic, you are looking at 375 HP at the crank... The 3.73 gears should actually show a reduction in HP, but also a reduction in 1/4 mile times.... Your 1/4 mile speed (much more important for tuning your engine than ET!) indicates approx. 330 HP at the crank (assuming the 20% loss again) your shift points may be wrong. You could be over or under running your peak power range. What kind of exhaust do you have, besides the headers? Don't worry about the 58 mm TB... It would be a waste of money to replace it with a 52 mm. What you need to think about now is the ultimate flow of things.... let me know what kind of exhaust you have and shift points I can help you from there

 

[69MyWay]

I almost wonder if you would not do better taking the car direct to a place like TPis etc, and paying them the $150, to $200 an your or so to slap it on the dyno and make pull after pull until they can calibrate the chip.

 

[UB2 SLOW]

I am currently running the shorty headers. I wanted to go with long, but being in the military, I may end up stationed in California, Hawaii or Florida, so I have to ensure I pass. I have Muffler Elimanators. The rest of the exhaust is stock. I was thinking about going with Flowmaster exhaust. If I can find someone with Software in NC, VA, SC, GA, or FL I would drive there to put the car on a Dyno. On a good note the car did run good enough to cook some rice. I raced the Acura, the guy who said Vettes were overated. My time 13.021 at 105.89 his 13.214 at 105.62. It turned out to be my best run of the night. I had a react of .610 he had a .595. After the race, I went over to tell him good race and he said that if he had not messed up on his shift he would have beaten me. I just replied next time and walked away.

 

[UB2 SLOW]

My shift points are currently set at 6200 with a 6600 rev limit. This is what Ed Wright had programed into it. On the Dyno sheet my horsepower starts to flatten out at around 6000. Peak HP(302) comes at 6000. Peak torque(300) was at 4500. at 6200 I have about 301 hp and 255 tq. I think I could raise it some.

 

[Vettelt193]

i hate ricers

shorty headers are fine with a cat-back exhaust... your current exhaust is a bottle neck though... your intake is very free, but your exhaust isn't... you aren't even really getting the benefit of the headers until you put on a good free flowing exhaust system. if you don't want to spend the money one one now, take it to a muffler shop and cut out the center resonator, replace it with straight pipe.... Your car will be very very loud, but will have more power.

How about the shift points? also, what RPM is your red-line set now?

 

[69MyWay]

If I can find someone with Software in NC, VA, SC, GA, or FL I would drive there to put the car on a Dyno.

You can call this shop.

Brent Frazier (904) 298-2447. They do $150 per hour on the dyno with an air fuel meter and will work with you and your budget until the power is maxed. It is about 5 minutes from my house. Right now you can't reach them until Monday 9/9/02. They are in the points lead in the local drag circuit and will be gone until then. They tune side by side with Rice. They however specialize in V8 power (Ford and Chevy).

If you come down, we could hook up and go terrorize the local rice crowd!

 

[Vettelt193]

where is your local drag strip? There is nothing that I have found over here in Tallahassee, and the closest I can go is gainesville raceway... I haven't done anything to my LT4, it is still new to me, and haven't even had a chance to get baseline numbers yet

 

[True Duals]

Tune Up

I have a guy who works on both my cars that lives across from the Air Station that does very good work

 

[Vettelt193]

ok, i got your second post... can you bump the shift points up 100 or 150 RPM? (or do you have to send it back to have it done?) Your second problem is when you do exhaust, your RPM range will go up even higher... and you are turning that LT1 really high as it is... I bet you don't feel any power loss at all on top before the shift, (which is good and bad) IMO, when you do exhaust, you will need to shift 100 RPM higher, and I already think you need to go 100 more as it is... this means you would need to turn a good 6400 to shift... add in 100 for slight error, and you are looking at 6500 RPM... I think that is a bit much for a stock LT1 bottom end... If it were me, I would actually feel safer with a 50 shot of nitros with a lower red line

 

[Edmond]

Hey, this is a great thread and thought I'd ask a few questions:

1. Gross vs. net HP figures are about 20% for auto's and 15% for manuals. What about the percentage of gross vs. net torque?

2. 1/4 mile time vs. speed. Which is a more accurate reflection of the cars power?

3. Is HP more useful than torque in 1/4 mile runs?

4. Should there/is there usually a proper HP to torque ratio?

5. Has the issue of weight elimination been brought up?

 

[Edmond]

You're disgusted at running a 13.021? I think that's a very respectable number to run.

 

[Vettelt193]

Good questions!

1. HP really isn't measurable, when you run a dyno torque is measured, then HP is calculated (HP=Torque x RPM /5252) so the power loss is the same

2. TRAP SPEED!!! If a car is setup to strictly run the 1/4 mile, it would use all of its gears, and all of its power to get to the finish... you could run really good times with not that much power if your car is geared strictly for running only 1/4 of a mile... So, since our cars are made to go much faster, we do not have maximum gear efficiency, so we don't get great 1/4 mile times, but our speed shows we have the power... it is really a complex mess of mathmatics

3. HP is the ability to make torque at a given RPM... HP is ony useful if you can run your car in your peak HP/RPM range... So, if you have no torque, and can't get into your peak HP range, you will do bad... 1/4 mile is all about a good combination of the two, and a good gear setup to match your engine.

4. depends on the car, and the car's purpose

5. no, but if one really wants to go fast, then it should... I like to be comfortable in my car, so I usually don't bring it up...

 

[Vettelt193]

You're disgusted at running a 13.021? I think that's a very respectable number to run.

I think UB2SLOW has just dumped a pretty penny into his engine... If I spent what he did, I would expect a timeslip in the 12's