This ought to settle the LT header issue

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Dec 16, 2003 | 09:03 PM

FELNGR8

Thread Starter

Melting Slicks

Joined: May 2002

Posts: 2,670

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From: Severna Park MD

This ought to settle the LT header issue

Is it worth it to go LT headers?

Here are my before and after dyno charts with a modded LT1 engine. The first dyno I had the LT4 Hot Cam Kit installed with ported heads, but still had the cast iron manifolds with a small cat-back exhaust. The curve is flat like an LT1 should be, and it doesn't begin to fall off till relatively high revs. But the torque and max power are disappointing.

Full size here: http://162.33.142.18/cars/DynoOne.jpg

Now for the after dyno results. The difference is TPIS long tubes with a full 3" custom exhaust, emissions legal with Random Tech bullet cats. My buttometer said the change was good, this confirms it.

Full size here: http://162.33.142.18/cars/DynoThree.jpg

I have never seen an LT1/4 dyno chart with a bump in the torque curve like this. I can feel the power come on when it hits this bump. Never mind the max rwhp being only 353, the operator cut it off at 5700 rpm because I haven't increased my rev limit yet.

50 ft lb of torque from LT headers, x-pipe and unrestricted 3" full exhaust. And it passes emissions testing with an early pass. I am more than pleased, I am ecstatic!!!

[Modified by 94lt1torchred, 8:11 PM 12/16/2003]

[Modified by 94lt1torchred, 8:14 PM 12/16/2003]

Dec 16, 2003 | 09:09 PM

Dark-Knight

Race Director

Joined: Feb 2003

Posts: 11,133

Likes: 1

From: ~The DARKSIDE Group~

Re: This ought to settle the LT header issue (94lt1torchred)

Good thing to confirm the butometer! :thumbs:

Dec 16, 2003 | 11:26 PM

VenkmanP

Safety Car

Joined: Apr 2003

Posts: 3,793

Likes: 9

From: VA

Re: This ought to settle the LT header issue (94lt1torchred)

Thanks for sharing! Your mods are roughly what I'm planning to do, so it's nice to see what I might gain. Great that you did it smog-legal. :thumbs:

Dec 16, 2003 | 11:31 PM

scorp508

Team Owner

Joined: Mar 2000

Posts: 83,383

Likes: 87

From: Boston, MA

Re: This ought to settle the LT header issue (steve9899)

You're just a little bit lean until 3000 RPM. I bet if you richened that part up a little you'd get rid of some of that bump and bring up the HP curve just a tad. You can see the drop in the curve go away where the A/F goes from about 14:1 to 13:1.

Dec 16, 2003 | 11:57 PM

crheinish

Burning Brakes

Joined: Nov 2002

Posts: 1,239

Likes: 1

From: Las Vegas NV

Re: This ought to settle the LT header issue (94lt1torchred)

:eek: Holy Headers Batman, that is one heck of an increase. :thumbs:

Dec 17, 2003 | 06:46 AM

FELNGR8

Thread Starter

Melting Slicks

Joined: May 2002

Posts: 2,670

Likes: 4

From: Severna Park MD

Re: This ought to settle the LT header issue (scorp508)

Quote:

So, it's back to John at Woodbridge Dynotech for a full tune. That will probably also smooth out the engine below 1800. I have a little bit of surging around 1700-1800. And he can tweak the ignition timing for me. Any prediction on how much more that would give me?

Dec 17, 2003 | 06:52 AM

jerkyboy

Melting Slicks

Joined: Jun 2002

Posts: 2,152

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From: Northern VA

Re: This ought to settle the LT header issue (94lt1torchred)

question for ya: Is Robert's exhaust I see in your sig the one in Woodbridge? Also, how much were your Random Techs and where did you get them? Thanks

Dec 17, 2003 | 12:53 PM

TIMSPEED

Le Mans Master

Joined: Mar 2001

Posts: 9,464

Likes: 1

From: Modesto CA

Re: This ought to settle the LT header issue (jerkyboy)

WOW! With the Headers/Exhaust you got a FULL 50rwhp gain! AWESOME!

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Dec 17, 2003 | 01:03 PM

Mad-Mic

Pro

Joined: May 2003

Posts: 682

Likes: 1

From: Annapolis MD

Re: This ought to settle the LT header issue

sweet gains!

i hope to get 25-35 hp out of my TPiS long tube headers i need to install :) when i do the headers and afpr i'm gonna dyno tune so i can get a chip burned.

don't know where you dyno tune at but i know a shop local that does 100 bucks an hour dyno tuning.

Dec 17, 2003 | 01:30 PM

#10

STL94LT1

Race Director

Joined: Jan 2002

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From: O'Fallon Missouri

Re: This ought to settle the LT header issue (Mad-Mic)

I am going to install EM long tubes and Random Tech cats sometime in early Feb. I am currently running Hooker shorties, factory cats, and a Flowmaster cat-back system. I will post the dyno results soon after the install.

94LT1', I will be happy with 1/2 the gains you recieved. Those #'s are incredible for an exhaust upgrade.

Dec 17, 2003 | 02:29 PM

#11

TuffShift

Racer

Joined: Sep 2003

Posts: 347

Likes: 6

From: Midwest

Re: This ought to settle the LT header issue (STL94LT1)

Quote:

94LT1', I will be happy with 1/2 the gains you recieved. Those #'s are incredible for an exhaust upgrade.

Incredible? More like "astounding"! I did more upgrades than that to my LT1 and don't have near the HP and torgue readings he got. I'd be interested in knowing what that rascal will do on the strip. That's where the "proof of the pudding" is really shown.

Dec 17, 2003 | 07:41 PM

#12

FELNGR8

Thread Starter

Melting Slicks

Joined: May 2002

Posts: 2,670

Likes: 4

From: Severna Park MD

Re: This ought to settle the LT header issue (jerkyboy)

Quote:

question for ya: Is Robert's exhaust I see in your sig the one in Woodbridge? Also, how much were your Random Techs and where did you get them? Thanks

It is Robert's in Woodbridge. He does good work.

The Random Tech cats cost $320 for the pair. I got them from Thunder Racing at a better price than from TPIS.

Dec 17, 2003 | 07:44 PM

#13

FELNGR8

Thread Starter

Melting Slicks

Joined: May 2002

Posts: 2,670

Likes: 4

From: Severna Park MD

Re: This ought to settle the LT header issue (Mad-Mic)

Quote:

I went to Woodbridge Dynotech. It's $75 per hour for tuning, plus a one-time $75 to install bungs for broadband data for tuning. He uses LT1 edit and LS1 edit for pcm cars. I don't know what he does for the earlier cars. He knows his engines and he knows his Vettes.

Dec 17, 2003 | 07:48 PM

#14

FELNGR8

Thread Starter

Melting Slicks

Joined: May 2002

Posts: 2,670

Likes: 4

From: Severna Park MD

Re: This ought to settle the LT header issue (STL94LT1)

Quote:

94LT1', I will be happy with 1/2 the gains you recieved. Those #'s are incredible for an exhaust upgrade.

Important to note, I already had ported heads and the Hot Cam kit. The exhaust change opens up things so the cam can work. The X-pipe is good for some of this increase.

Dec 17, 2003 | 07:56 PM

#15

FELNGR8

Thread Starter

Melting Slicks

Joined: May 2002

Posts: 2,670

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From: Severna Park MD

Re: This ought to settle the LT header issue (TuffShift)

Quote:

I got a 12.9 on my first time out while figuring out how to launch it, and on an 80+ day. WIth DRs I do expect to get to 12.5. With practice maybe a little better.

I don't want to see much better than 12.5s this spring cause then I'll have to spend on gears. Is there any cure for this modding disease?

Dec 17, 2003 | 08:09 PM

#16

scorp508

Team Owner

Joined: Mar 2000

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From: Boston, MA

Keep in mind that his car his not stock and has an aftermarket cam & heads. These results are not typical, it just shows how much his whole combination was choked.

Dec 17, 2003 | 08:33 PM

#17

FELNGR8

Thread Starter

Melting Slicks

Joined: May 2002

Posts: 2,670

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From: Severna Park MD

Re: (scorp508)

Quote:

These results are not typical, it just shows how much his whole combination was choked.

Exactly what John told me when I dynoed last spring. But he told me exactly what this exhaust would do for my car, and I took his advice.

I am running much leaner than the other big HP cars at the dyno day. My car does not blow a mosquito killing cloud like the others do at revs. fdupny's Z06 is much richer than mine on his chart, and he was making us back away from that thing. But what a sweet sounding car he has with B&B pipes.

The question is, is it too lean for safety (probably not), and as you said am I giving up power without the tune? Probably am.

One other difference, I have hand ported heads and I requested a street setup. Vs. CNC heads from other sources. So my porting probably matches the Hotcam and LT1 intake better in this rev range than CNC heads would. The whole thing together works well.

Dec 17, 2003 | 08:43 PM

#18

scorp508

Team Owner

Joined: Mar 2000

Posts: 83,383

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From: Boston, MA

Re: (94lt1torchred)

Quote:

The question is, is it too lean for safety (probably not), and as you said am I giving up power without the tune? Probably am.

I think you have power to be had richening it up a little bit, but how much I'm unsure of. I think the HP curve won't have that very slight dip in it in the beginning. The torque curve I think will raise itself some up to about where the A/F comes back to somewhere around 13.1:1 making the "hump" not as dramatic.

Dec 17, 2003 | 08:58 PM

#19

FELNGR8

Thread Starter

Melting Slicks

Joined: May 2002

Posts: 2,670

Likes: 4

From: Severna Park MD

Re: (scorp508)

Quote:

I have another dyno chart done at Carlisle with A/F that I didn't post here. It was with the old exhaust setup and I was much richer then at the top end than I am now. I could see my exhaust blow stuff (not black) on the truck there, this time I did not see any change in the exhaust. But we were doing this dyno at freezing temps last Saturday. Would the cold change the tune that much?

[Modified by 94lt1torchred, 7:59 PM 12/17/2003]

Dec 17, 2003 | 09:10 PM

#20

scorp508

Team Owner

Joined: Mar 2000

Posts: 83,383

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From: Boston, MA

Re: (94lt1torchred)

Quote:

Would the cold change the tune that much?

Well, not by all that much. It will help make more power with the cool dense air, but the air/fuel ratio readings will be the same. As long as your charts are SAE corrected then that'll tell you what you'd make on a normalized day.

It makes sense that you are leaner now on the top end than before. The headers help the scavenging affect and pull more gases from the cylinders leaning them a little.

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