Today I dynoed my '91 Z for the first time since bone stock. These numbers are good enough to make most people skeptical, but hopefully it will show some budget modders that you can spend less money and get more of a result out of a stock L98. First things first:

The car: '91 Z28, auto, 3.23, 5.7 TPI, 75k on motor and trans.

Bone stock dyno with ****ty fuel filter and old plugs: 176 rwhp, 248 rwtq. (November of 2001)

This is exactly what is done to it now:

Ported plenum
Cut airbox with K&N's
Relocated MAT (to airbox)
air foil
Adj. fuel press. reg.
TPIS plug wires
Bosch Platinum +4's
Base timing advanced to 10 degrees
No cats
No smog stuff
SLP catback
LS1 aluminum driveshaft

First pull- Air filters in, fuel pressure 45 psi:
231 rwhp, 339 rwtq

Last pull- Removed intake box except for the piece that connects to the throttle body, fuel pressure 37 psi:
242.8 rwhp, 353.6 rwtq

This just goes to show that you never know where you're at in your state of tune without a dyno. The motor wanted the least amount of fuel pressure I could give it. By the way this was on 89 octane gas with the stock chip. I have all the dyno graphs but I need help posting them. Stay tuned.

 

Wow! That's excellent!

 

The coolest part is that all these mods cost less than $1000 total.

We did 11 dyno pulls and found out that my dirty K&N's were robbing about 7 hp, and the factory intake duct is a little restrictive as well.

 

Those are great numbers for the for those mild mods... more suprising is the engines desire for a a lower fuel pressure. Really cool - happy for you.

 

Can you give me some details on that relocated MAT, how is it done?

 

I would not relocate the MAT unless you are going to reprogram the PROM to compensate. It may give you more hp or it may take away hp (depending on your setup and how your engine is running. My brother tried it on his 92, and it made the engine run sloppy at WOT, to rich.

http://www.gmtips.com/3rd-degree/dox/tips/mat/mat.htm

 

Not sure how much the MAT reloc. does on a speed density car. It just gives the computer an accurate reading of the actual air temp before it goes into the engine. The stock sensor is inside the plenum, and it gets heat soaked in there so that's not a true to life reading. That could very well be one of the reasons I was running so rich though and why I had to decrease fuel pressure.

 

If you're going to do a MAT relocation on a SD car, you do pretty much need to account for it inside the PROM. The stock chip is calibrated for a heat soaked MAT. In cooler weather, a relocated MAT will indeed just make you go richer. In really cold weather, the effects are so serious that you'll bottom your BLMs rich if you don't adjust the chip.

I haven't actually done any tuning with my MAT table, i'm just using one that Glenn91L98GTA posted a long time ago. Works pretty well for me from what i've seen on it so far, BLMs stay in the same range in all the temps i've had a scan tool on it in (sub 30 to 70) Before the new MAT tables i was pretty close in the heat of summer, and way fat in the winter.

Thats why everyone loves MAT relocations. Rich always FEELS faster. People that actually tune or go to the track can give you better answers though then butt dyno experts. Would i recommend a relocated MAT. Absolutely, definitely helps with teh heat soaked feeling you get when the car has been sitting in traffic in the summer/staging/etc. But along with it, you have to compensate in the chip too so that you're not way off in cooler weather. But considering the low cost of PROM burning equipment, i don't think it's a big deal, especially considering all of the things it gives you access to.

 

Hmmm, good info Ed. Since higher fuel pressure atomizes better, I wonder if I'd get an even better result by putting the MAT back in the plenum and cranking the fp back up.

 

Where is the MAT? i have seen people with it in the air box.. but i dont have it there? i dont know where it is? there is no harnes that extends to there, there is nothing... can someone tell me where it should be? I have seen it on the side of the Y intake in other cars, and then i check mine, and its not there, only what looks like a patch over a hole... i dont know whats up with that?

 

Like my above remark says, back in the plenum. It plugs into he underside of the plenum in the back.

 

Nah. The whole higher FP = better atomization thing doesn't really make that big of a difference in the end. Maybe i'll do some concrete testing later this year to prove it, but i've never noticed a difference between running high FP or low FP, both compensated in the chip.

Since you seem to be into the budget approach, why not just get into prom burning instead. Thats where you get cheap power and a real understanding of what the ECM is trying to do.

 

No chip burning for me on this combo. It's not worth the headache until my big power parts go on. And the only reason I've been into the budget approach is because I've been a slave to a $600/mo. lease payment on a '99 C5, so I was always broke (dumb, dumb dumb decision).

But now it's time to have fun. This car is now getting set up for full blown drag racing. 70/30's in front, 50/50's in back, with slicks and skinnies. I am going to spray nitrous on this setup with a 3000 Yank torque converter. When the rear, tranny or engine breaks, it will immediately be replaced with something bulletproof. It'll be fun to see how long everything lasts.

 

easier to learn when you're pretty much stock.

there's also a lot you can get out of a converter with a little spark curve work. Complete control of when and how it hits.

And a big shot of nitrous.

Thats exactly the kind of reasons i used to get into prom burning.

 

Hey Ed- What's the highest dyno you've ever seen from an L98 with stock TB, runners, base, heads, cam, manifolds? I'm wondering if there's anything left in it?

Also, if I email someone the dyno file can you post it? I have no clue.

 

My bad, man! thanks bro... now i gotta go look for it

 

Tough to say on the dyno, but those are some damn nice numbers either way.

As for posting the graph, if it's a picture file like a .jpg or .gif, just go to the attach file thing below where you type and browse to the picture. If it's something else, you'd need to do a screenshot and then make thata picture and post it.

 

What Dyno did you use and were those SAE Corrected numbers?

 

Dynojet 248

SAE corrected- 242.81 rwhp @ 4350 rpm (about 1000 ft. elev.)

SAE uncorrected- 236.33 rwhp @ 4350 rpm

 

WOW!! That is impressive for the mods!

 

Well done on the increase - pretty impressive stuff.

Pity you can't do the chip until after more mods though.