Hit a tuning wall. Any suggestions?

[Fred 86 GN]

My 3700lb GN ran 111mph (390hp) with a JL93 chip (19° timing) at 19psi boost and 48psi fuel. Octane at about 101 from 50% 94 and 50% 110.

It has recently ran 113mph (410hp) with a Reds100 chip (27° timing) at 20psi boost and 45psi fuel. Octane at about 108 from 50% of the above mix with 50% C-16 116.

In both cases, the DirectScan output has shown about 2 degrees of knock retard in the near the top of third gear. That seems to be on the "hairy edge" of tuning to me. What more can I do to get more power out of the engine with less or no knock retard???


The engine stays under 180F throughout the runs. MAT temps are in the 80's through most of the runs.

Mods -- TE-44, CAS V4, 009 injectors, THDP, Hooker exhaust, cold air induction, RJC plate, 340 pump hot-wired, AC 42 plugs.

I want to make more power! Help!

 

[Russ Merritt]

Put AC r42ts plugs, or (I used with my irons) autolight 23s, Are you set on using this chip? If not get Reds 106 and turn it up!

 

[TurboDave]

One other tip, stop trying to mix "magic" brews of race gas. You really DON'T know what the octane is you're running. Oh I know, you may think you're sure about it, but think about it. Do you really?

When at the track, run pure race gas, Unocal 114 or better. No mixing/matching. Drain the tank through the fuel rail, and but in 10 gals of good race gas only.

 

[topfuel]

"hairy edge" no doubt

I always feel like my connecting rods are going to come out and
pay me a visit in the top of 3rd gear with everything spinning so
fast and working so hard

Just curious Fred, where are you're O2's at in the top of 3rd?

Also, did you notice an improvement in performance after you
installed your powerplate? More boost with no knock?
I just ordered my powerplate and I was hoping to
kick it up a notch on the boost

 

[bruce]

Originally posted by Fred 86 GN
In both cases, the DirectScan output has shown about 2 degrees of knock retard in the near the top of third gear. That seems to be on the "hairy edge" of tuning to me. What more can I do to get more power out of the engine with less or no knock retard???
The engine stays under 180F throughout the runs. MAT temps are in the 80's through most of the runs.
Mods -- TE-44, CAS V4, 009 injectors, THDP, Hooker exhaust, cold air induction, RJC plate, 340 pump hot-wired, AC 43 plugs.
I want to make more power! Help!

It's money time.
You have two real choices, a Translator Plus, or ME, and getting enough injector to support some more HP. 55s should be OK, unless you are gunning for some real big HP.

You quoted having a Scanmaster, I'd bet you injector pulse widths are are 100 or more %.

 

[Russ Merritt]

I disagree on "money time" He has more left, just gotta find it. He has enough injector for 510HP. You don't have to ditch the MAF to go 11s. I agree with not mixing fuel, getting a real race chip (reds 106) colder plugs, and REAL fuel will get him the MPH/HP

 

[bruce]

Originally posted by Russ Merritt
I disagree on "money time" He has more left, just gotta find it. He has enough injector for 510HP. You don't have to ditch the MAF to go 11s. I agree with not mixing fuel, getting a real race chip (reds 106) colder plugs, and REAL fuel will get him the MPH/HP

42s
we'll give you 1.2 for the increase in injector size per fuel pressure change due to boost.
That's 50.4
times 6
302
times .6 BSFC
503 at 100% DC
now by .85 to get a reasonable DC, and at best you'll be at 427 HP.
If you want to bend the numbers, they will bite back eventually.
But, you'll find lots of agreement, for doing things the hard way.

 

[CraigT]

Concur with TurboDave, run the pure gas.

 

[Russ Merritt]

Jeez, That's strange then. I went 115MPH in my 3636# GN with little 40# injectors? The run was 11.57 with a 1.58/60' I know et is all launch but 115/3636# is more than 427 isn't it? I can't remember the formula I used but I thought it was more than that. That was then (98)

 

[Mile Hi GN]

I agree with Turbo Dave.

I have never understood the thinking behind subjecting a $3,500 to $5,000 motor to the stress of a full boogie 1320 and doing it on some street gas / race gas combination.

Save the street fuel for the street, drain the tank (it takes about 5 minutes) put the pure race gas in, go with a pure race chip and see what the car has got.

I guarentee you, you are leaving tenths and MPH on the table until you do.

 

[Fred 86 GN]

Guess it is time to start trailering the car...

Thanks for all the suggestions!

My O2 numbers were 750-780mV with the JL93 chip all through third gear. That chip seems to limit the injector PW to 80-85%, so the car was running out of fuel I think. Static fuel pressure was 48psi.

The O2 numbers for the Reds100 chipe were 780-800mV all through third gear. That chip definitely provided more fuel.

I only have a JL110 chip and a Thrasher 108 for "full" race chips to try. Think that one of those will do better than Reds100?

The spark plugs are AC42's, sorry for the error.

I am not trying to mix a homebrew...it just happens to be what I had in the tank at the time. Does pumping the tank down (two gallons left in it using the fuel pump?) really make a big difference? When I put in the C-16 on top of mostly Turbo Blue race gas already in the tank, I thought I would have plenty of detonation resistance. Appearently not...

10 gallons of C-16 is like $90! I suppose for a "numbers" run it would be worth it. I certainly do not want to drive 40 miles to the track and back on that expensive fuel. It seems a trailer is the way to go -- slicks, pure $$$ race gas, and a trailer.

Before I try the all-out run, I need to find some traction! 28x10 ET streets sound about right?

Thanks,

Fred

 

[azgn]

actually, you can get by very nicely on 28X9's with no fitment problems ( i have run 60' times in the 1.4x range with them and I launch off a t-brake at 15+ lbs)

FYI, my car ran its best times with Red's 100 chip when I had a TA-49/Blue tops...was consistent 115...never could get the 106 or 108 to work well.....you can run more boost with the 100 chip (less timing) easier to tune without all that timing in the way

 

[DonnieShort]

Need to drop that 60' time down off that 1.92. You didn't mention what tires you're running. If you don't have slicks, get some. The e.t's will come down after that.




Donnie

 

[jetmech]

Hey guys, someone said to get ac42 plugs, I thought our cars like the cr43ts plugs. Im buying a set this week. which ones should i get. Also i will be installing 36# injectors in a couple weeks. if that matters on plug choice. thanks rich

 

[Russ Merritt]

43s for street,42s for race 20+#boost

 

[jetmech]

I am mostly a weekend cruiser, probabley 2000 miles a year, would the 42's be okay for the street or put 43's in and before i drive to the track put the 42's in. and are they cr42ts or a different #

 

[Russ Merritt]

They would be fine, they might load up a little cause they're so cold but should be OK. Just clean em off with the gas pedal every now and then

 

[jetmech]

thanks russ, i will try the 42's this weekend and im going back to my thrasher 100 chip. Hopefully going to get that 12 sec. time slip. Im not having luck w' the t-108. But last time out it was 95 degrees. I will try them both (chips)

 

[U1ARUNIT]

As you are figuring out already you need a RACE chip for RACING! They usually have more timing, but ALSO more FUEL. Don't mess with street chips on the track as they are for the street (and don't allow enough fueling).

009 injectors are plenty for what you are running now. My car ran almost 118 mph on them with a RACE chip(Reds). But, I have since stepped up to the bar with 55's, Translater +, and Extender and I am loving life! Car idles and drives better than a stocker with this setup.

 

[Chuck Leeper]

Traction??

I'd forget adding more HP until I sort out the suspension.. why the bucks in the engine and added HP, when a decent 1.60 range short time will net you an easy 11 sec time slip..??
Take .3 off the 60 and you will see a dramatic drop in ET.. in the neighborhood of .5 sec or even better.
If you are serious on the strip performance, skip the ET streets and go DIRECTLY to slicks, like Woody said...28 x 9 is a good start.