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Changed 58mm for 48mm, raised fuel from 44-47psi and put on Ram Air

U

UB2 SLOW

Guest
Okay everyone, I dont have official results, but after taking your recommendations about swapping the 58mm to the 48mm, raising fuel pressure from 44 to 47 and putting the Ram Air on. The car feels allot stronger. The response is quicker also. I took the car out and did a 1/4 mile run with the G-tech. It showed 12.9 @107. The best I could do at the track was 13.02@105.89. Assuming the G-Tech is accurate, that is a big difference. The car is still sluggish below 2500 rpm. I think this is due to the LT4 Hotcam. I will swap the BOSCH for Autolites later. I am also thinking about going with a Cat Back instead of the Eliminators. What do ya think? Good or Bad Idea.
_______
 

BigRed

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Joined
May 23, 2001
Messages
948
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Edmonton
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1985 Bright Red Rocket
Now Im still learning here but is there a way of advancing the timing so your not so sluggish off the punch?

I know onw way that'll guarantee a LARGE difference in acceleration. Use a Aftermarket Ignition box it'll deliver 60% more spark plus fire each plug not once but three times. I put the MSD 6A on my car and WOW what a difference.

Also my friend bought a 91 Stepside and he said out of all the mods he did to it (He spent like 4000) the MSD was the most noticable difference.

And for like 250 Bucks (300 with a Coil) you can't go wrong. You'll be pleasantly surprized.
 

BigRed

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May 23, 2001
Messages
948
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Edmonton
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1985 Bright Red Rocket
Oh not to mention your going to GAIN fuel mileage! And I mean ALOT.

My car used to run around 21-23 MPG on the highway now its 25-28 MPG. It took me 1 1/2 tanks to get from Vancouver BC to Calgary Alberta. (If your not sure how far that is look at a map your be impressed.)
 

FX GS

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Feb 24, 2001
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639
Location
Camp Hill, PA
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Formally Callaway SuperNatural Grand Sport #0001
If you don't mind another suggestion, I would go with the NGK
TR55 spark plugs and why your at it, replace your plug wires with MSD 8.5 Super Conductors.
 
U

UB2 SLOW

Guest
The only way I could advance timing would be to reprogram the computer. I dont have the software or the equipement to do it. I am still looking for someone in the area that does.

I am going to look at autolite and NGK this afternoon. Do you know what they cost?

I have been thinking allot about the MSD's. I plan on putting a supercharge on next. How will that combo work together? I only plan on runing 6-8psi boost due to a 10.2 compression ratio. If my math is correct, with 6-8psi I should have over 500hp at the crank and 430 at the wheels. This should put me deep in the 11's.
 

WhalePirot

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Joined
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Messages
2,942
Location
SoCA
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1984 White Z-51/ZF6-40/Shinoda body
GM plugs for GM engines

You can time the engine, static, after putting the ECM ignition timing in bypass. It is a brown wire on my car, near the distributor. The ECM assumes that this static advance is whatever the emission tag calls for.

I find the Delco plugs in my 406 work very well. Don't recall the #; sorry.


Anyone need a set of slightly run, Accel 265S plugs?

I may, also unload my unused MSD 6. I don't need it.

:w
 
U

UB2 SLOW

Guest
Got a new problem with the car. After raising the fuel pressure to 47 from 44, I now get codes P0171/P0174 system too lean, bank 1 and 2. I raised the fuel pressure to 48 and the idle increased and I still got the same codes after 50 miles. Any suggestions?
 

Edmond

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Joined
Aug 1, 2001
Messages
5,218
Location
Louisiana
Corvette
2003 Z06
You could probably find someone to swap that 58 for a 52; look around. There's probably some guy out there who has a nice 52 that wants to upgrade to a 58.

I read that the Vortex is good for two tenths off the 1/4. There are a couple of reviews here in the forum for it.

If it were me, I'd stay with the eliminators instead of the catback.
 

BigRed

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Joined
May 23, 2001
Messages
948
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Edmonton
Corvette
1985 Bright Red Rocket
What have you done about your O2 sensors? With all your mods especially regarding exhaust your O2 sensors are going to freak! TPiS sells a cheater plug to deal with them so they trasmit normal readings.

The MSD will actually complement the supercharger. With the added air your going to have added fuel so wouldn't be a good idea to have added spark? All the Twin turbo tuner guys run MSD's.

I run a MSD 6A, MSD 8.5 Wires, MSD Blaster 2 coil, Bosch Plat four plugs and Im very happy.
 
U

UB2 SLOW

Guest
I think I will looking for an MSD in a couple of months. I am really strapped for $ after all of the mods.

I think I have found someone willing to swap TB's. If so great. If not Look out ebay!

Do the cheater plugs affect emissions?
 

Mad-Mic

Gone but not forgotten
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Feb 12, 2002
Messages
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Annapolis Maryland
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1987 Redskin Red Coupe
i run the bosch plat +4 plugs and man what a difference! car is strong all the way to 5000 grand but still got all stock stuff on her. this winter i'm gonna start modding it pretty good :D

UB, you can put a thicker gasket on for your heads if your gonna do the whole upper end (would be wise for the supercharger0 this will give you around 9.5 to 1 and a good piece of mind. superchargers are hard on the valve train!
 
Joined
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Tallahassee, FL
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none right now :(
with the top end done up like you have it, you can kiss your bottom end goodbye with 6-8 psi... You have to realize a couple things about superchargers... when you buy one from a company, they are figuring your car is stock... so when they send you a pulley rated at 8 psi, and you put it on your high flow intake/heads etc. it will look like maybe 4 psi... Your setup, with a 6 psi pulley is how a friend of mine blew up his LT1 (and it only was showing under 4psi of boost). If you plan on supercharging, you have to stay under 5 psi because of the cam and heads.

about the codes.

I think your fuel pressure is so high now, the computer is fighting back with a shorter pulse... this is causing a bad spray and burn, so the computer thinks it is lean.... even when it tries to increase pulse, it gets a bad spray, further confusing the computer... since it increases pulse length without a better air/fuel mix, the computer thinks the pressure is too low. when you tuned the fuel pressure did you reset the computer first? It isn't easy getting the right pressure, especially since the computer runs differently when it is cold, when it is idling etc.

about MSD

LT1/4 engines have very good ignition systems, even with your setup, MSD is a waste of money. I have never seen an LT1/4 run faster with one, even with superchargers or cars set up like yours (L98 is a different story though)
 

Edmond

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2003 Z06
So it would be useless to use the MSD on 92 and up while 91 and down would benefit? What kind of benefits would the L98 get from the MSD?
 
Joined
Jun 20, 2002
Messages
2,509
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Tallahassee, FL
Corvette
none right now :(
the stock L98 ignition is fine for stock to mildly modified cars, but when you start getting into things, a modified ignition system can really help... all it does is make a better spark, so a cleaner burn... generally resulting in more power only if your engine isn't getting a solid burn as it is.... basically, if you start getting into fuel pressure adjustments on an L98, you could benefit from a better ignition.
 

Edmond

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Messages
5,218
Location
Louisiana
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2003 Z06
Okay, so the lesson from all this should be that no matter how many mods and adjustments you've made, it all won't benefit much unless you get the brains in the car reprogrammed to work with the muscle. Am I on the right track here?
 
Joined
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Tallahassee, FL
Corvette
none right now :(
Tuning is the biggest way to get horsepower from your engine... but, I have to throw a couple more curve balls at you as well... first off, the older your C4 is, the less the computer can do, and the slower the computer is... Tuning a computer on a 1985 Vette doesn't do nearly as much as tuning one on a 1995 Vette. So, the older your vette is dictates the amount of mechanical Vs. computer tuning.

not only do you have to have a good tuning, but you have to have parts that work well together... You can throw all kinds of money at your car and get very little benefit out of it if you don't do the right combination, or you have a bottleneck in the system... When I look at a car, I start at the intake, and work my way through the system to see what is going on... UB2SLOW has a good intake, good manifold, heads, rockers, cam, and headers... when you look at the overall picture though, it is breathing through a 48 mm throttle body, and a half stock exhaust... When he gets his car dialed in, he will have a bigger TB, and a better exhaust... those are the two bottle necks in his system. You can have the best flowing heads in the world, but if the air has to get through a tiny TB first, they won't do any good... IMHO, the biggest gains UB has made are in the gears and stall converter. Not a bad thing, because as soon as his engine is dialed in, he will have one big bad LT1.
 

vettn94

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Joined
Aug 9, 2002
Messages
181
Location
Warrenville, IL.USA
Corvette
1994 Polo Green Convertible
Vettelt193 said:
I think your fuel pressure is so high now, the computer is fighting back with a shorter pulse... this is causing a bad spray and burn, so the computer thinks it is lean.... even when it tries to increase pulse, it gets a bad spray, further confusing the computer... since it increases pulse length without a better air/fuel mix, the computer thinks the pressure is too low. when you tuned the fuel pressure did you reset the computer first? It isn't easy getting the right pressure, especially since the computer runs differently when it is cold, when it is idling etc.
about MSDLT1/4 engines have very good ignition systems, even with your setup, MSD is a waste of money. I have never seen an LT1/4 run faster with one, even with superchargers or cars set up like yours (L98 is a different story though)

If I remember correctly from the original post, he still has #30 injectors in the car, which IMO are way too big. If you are already dumping too much fuel in @ 44psi then why would you raise it ? The fact that the car is flat in the lower rpms is a clear indication the car is running too rich ( I know the code says lean exhaust now but read the explaination above ).

A supercharger ,MSD box, or bigger throttle body is not going to solve the problem.
Getting the right injectors and tuning in the car will.
just my .02 again
 

-=Jeff=-

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Joined
Feb 2, 2001
Messages
909
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Bartlett, IL. (Chicago Suburb)
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1990 ZR-1
Vettelt193 said:
with the top end done up like you have it, you can kiss your bottom end goodbye with 6-8 psi... You have to realize a couple things about superchargers... when you buy one from a company, they are figuring your car is stock... so when they send you a pulley rated at 8 psi, and you put it on your high flow intake/heads etc. it will look like maybe 4 psi... Your setup, with a 6 psi pulley is how a friend of mine blew up his LT1 (and it only was showing under 4psi of boost). If you plan on supercharging, you have to stay under 5 psi because of the cam and heads.

about the codes.

I think your fuel pressure is so high now, the computer is fighting back with a shorter pulse... this is causing a bad spray and burn, so the computer thinks it is lean.... even when it tries to increase pulse, it gets a bad spray, further confusing the computer... since it increases pulse length without a better air/fuel mix, the computer thinks the pressure is too low. when you tuned the fuel pressure did you reset the computer first? It isn't easy getting the right pressure, especially since the computer runs differently when it is cold, when it is idling etc.

about MSD

LT1/4 engines have very good ignition systems, even with your setup, MSD is a waste of money. I have never seen an LT1/4 run faster with one, even with superchargers or cars set up like yours (L98 is a different story though)

I agree completely with this..

Return the FP to 44 PSI. since you have 30# injectors you at dumping too much fuel. Call the guy the programmed your car and see what he set your injectors for. that may be part of the problem.
 

WhalePirot

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Messages
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Location
SoCA
Corvette
1984 White Z-51/ZF6-40/Shinoda body
the lesson from all this should be that no matter how many mods and adjustments you'v

BINGO!

Also, check this link for injector sizing and fuel pressure effects:

http://www.jimsperformance.com/tech.html

Also, my expert claims no gain from an MSD box until past 6500rpm. Says that the ignition fires only what is needed to fire the plug, so how much overkill do you care to pay for?

The HEI is fine for most of our cars; runs my 406 real well to redline, and real strong down low.

I like BANG for MY buck, and this guy KNOWS Corvettes and what works and what is EGO bought. A refreshing change from most 'experts'.

:w
 

maxrevs85

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Joined
Dec 17, 2001
Messages
709
Location
Eaton Rapids, Mich
Corvette
!985 ,blue coupe, 4+3 Z51
I dont get it:duh Do you need to know your Hp to use this chart? I missed something. I like to figure what he says is correct for my engine.
 

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