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Discussion Starter #1
I was initially disappointed with my dyno numbers back in Sept when I got my heads, cam, headers and pulley installed. LS1speed was kind enough to let me come back and test a few things tonight to see if they could find a way to let out some more ponys. We tried disconnecting the stock catback and running straight out the headers. We also tried running with an SLP screenless MAF sensor. The results were less than spectacular. With absolutely no Cat back installed I gained 6 hp. and the slp maf sensor netted me nothing. Now to be fair we didn't optimize the tune for each of these runs, but it was obvious that we weren't going to get much.

The good news is with the better conditions and after letting my car run with these mods for the past month I gained about 14 ftlbs of torque and 4 hp since the last time I was there. The dyno graph is attached. I'd like to say a big thank you to LS1speed for letting me do all this (especially on a Sat night).
 

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curve still looks very strong. Fuel curve looks great as well. I guess this means you aren't a player when it comes to an exhaust huh?
 

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I guess this shows the exhaust is pretty good stock
 

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May I quote you on that?
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Dbluegoat said:
I guess this shows the exhaust is pretty good stock
It would seem that there are no glaring weaknesses (except heat soak) on this car. We've gotten enough charts on individual changes; CAI only, Header only, Catback only, etc. to see that they all contribute their small part. LigTen is getting pretty nice performance with R/T cats and a CAI using the stock exhaust manifold. I'll be very interested to see what Doug gets swapping the JBA's for the LT's. All in all, it seems like to stock GTO is reasonably well-balanced, and for huge numbers, you have to attack it on multiple fronts.
 

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Doc, Just Doc
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CJ,

With the 5.3 heads and the higher compression I would suggest an alt. fuel tank setup with race fuel 110-116 and a switch for the computer to use that fuel. I have seen that done and the HP gain is quite impressive. The higher compression motor is affected more by octane then a lower compression!

Great numbers and nice torque too!

Doc
 

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mistermike said:
It would seem that there are no glaring weaknesses (except heat soak) on this car. We've gotten enough charts on individual changes; CAI only, Header only, Catback only, etc. to see that they all contribute their small part. LigTen is getting pretty nice performance with R/T cats and a CAI using the stock exhaust manifold. I'll be very interested to see what Doug gets swapping the JBA's for the LT's. All in all, it seems like to stock GTO is reasonably well-balanced, and for huge numbers, you have to attack it on multiple fronts.
Yes the most glaring thig to me is the heat and intake setup. I dont plan on changing the exhaust it sounds perfect to me.
 

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Doc, Just Doc
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Also about the exhaust, good info! This is why i went with the JBAs to the Random Tech cats to the stock cat-back. I think this will be a nice setup wit the K&N CAI, plugs, wires, and a dyno tune! They get installed on Tuesday and hopefully a dyno the Friday after!

Doc
 

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Dbluegoat said:
Yes the most glaring thig to me is the heat and intake setup. I dont plan on changing the exhaust it sounds perfect to me.
It's the best stock exhaust sound I've ever heard.
Must be nice being blown by Maggie. ;)
 

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Nice sunset Dblue.

I've always been a fan of torque numbers over HP. Looking at Dblue's numbers and CJ's numbers, it looks as if the Maggie would be the way to go for me. But I'd rather run a cam for the old school lope. I'm not a cam expert by any means. It seems that every one is running the same cam. Has anyone tried a different cam? I've only heard one car run, DY's, and it sounded sweet just about perfect as a matter of fact. I personaly could deal with a slightly lopieer (sp?) cam to get a stronger low end/ middle range torque curve. I have a bit of time to wait. I'm not doing anymore work until spring. So I have to give a hardy thank you to everyone who has done the expiramenting and first installs. Has anyone out there installed a different cam with better torque results?
 

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Doc GTO said:
CJ,

With the 5.3 heads and the higher compression I would suggest an alt. fuel tank setup with race fuel 110-116 and a switch for the computer to use that fuel. I have seen that done and the HP gain is quite impressive. The higher compression motor is affected more by octane then a lower compression!

Great numbers and nice torque too!

Doc
The compression ratio is still adequate for 93 octane. Adding octane is not going to help anything but go thru 02 sensors.
 

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That makes feel better about keeping my stock exhaust too.
Wish my Tq #s were higher, but I was able to take it to the track Saturday.

Conditions: Horrible 40deg. Rain 30mph head wind.

Results: Not bad for no practice .
Best run out of 3:
12.870 @ 110.36mph
2.069 60'

I spun em bad in every gear. I'll post some videos later.

I think I can get it into the lower 12s with some more practice and traction.

I need to re-learn how to drive this thing now. The RPMs come up so fast..
 

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Discussion Starter #12
bclarke said:
That makes feel better about keeping my stock exhaust too.
Wish my Tq #s were higher, but I was able to take it to the track Saturday.

Conditions: Horrible 40deg. Rain 30mph head wind.

Results: Not bad for no practice .
Best run out of 3:
12.870 @ 110.36mph
2.069 60'

I spun em bad in every gear. I'll post some videos later.

I think I can get it into the lower 12s with some more practice and traction.

I need to re-learn how to drive this thing now. The RPMs come up so fast..
I'd love to go to the track with you, I think we'd have one hell of a race. :)
 

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Did you check to see if your throttle body opened up all the way? Mine only opens to about 85%!
 

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Discussion Starter #14
Mine opens all the way to the stop. I think I tested it with the predator and saw 100% but I'm not sure.
 

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Interesting note:

While browsing the Viperclub forums, I noticed that the dyno sheets for a GenI Vipers looked very similar to this one. Kinda cool how a GTO with a few $K in mods can equal (in dyno #s) a V10 Viper. In our ever-growing lust for more HP, it's interesting to stop and think *just how much power* this really is...
 

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cjlannoy said:
Mine opens all the way to the stop. I think I tested it with the predator and saw 100% but I'm not sure.
See the stop is the problem, it holds the Throttle blade to about 85% throttle or about a 78 degree angle, not flat. The TPS will show 100% since it's calibrated at that value, but I picked up 12 horse at the tires by bending the stop to let it open all the way.
 

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Gaining 6hp from removing the cat back doesn't quite say the stock cat back is really good, some mufflers flow better then straight pipes. Though the addition of a cat back may only be good for 6rwhp over stock pipes.
 

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Discussion Starter #18
To me 6 hp or even 10 doesn't really justify spending the extra money for the exhaust and tuning plus the added noise. (I really like the way it sounds now) I'm pretty happy that I'm not loosing 30 hp or something like that. :)
 
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