98_1LE

About what kind of gains in power/ET could be expected from SLP 1.75" headers, SLP 2OTL cat back and a high flow cat ove the stock exhaust? The motor is basically stock.

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87 Formula 350 13.94@96.67
98 Z28 1LE 13.15@107.59
1LE Owners Association

The ODB

I have recorded gains of 7 tenths and 5mph on my 86 305 swapping from stock exhaust to TES headers, hollowed CAT and a cutout.

If you ditch the cat and run a cutout I would expect about the same % power gain on yours. Otherwise your CAT and muffler are going to goof up the gains from the headers and the total power will be less than its potential.

JPrevost

I understand the headers, I understand the cat-back system, I just don't understand so many people getting rid of the cat.
My personal opinion is the air sucks, why make it worse, keep the cat if you're a daily driver, ditch it if it's a serious racer.
Not like the Cat was that stupid of an idea, just get a high flow 3" unit.

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, Jon (91 RS too many mods to list)

james_fearn

I second that. I don't understand why people trash their emmision stuff for 5 hp. If they are worried so much about 5 hp than their are better and more legal ways of doing so.

James

IROCZTWENTYGR8

iTrader: (1)

I agree, kinda.

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Looking For:

87 IROC-Z 350 TPI
84 TRANS AM 305 H.O.

[This message has been edited by IROCZTWENTYGR8 (edited March 07, 2001).]

JETHROIROC

The cat is the next bottleneck in the system after the manifolds, and therefore changes made there have more potential than if changes were just made to the cat back. Plus they are expensive and not all of us (especially with dual cat systems) can afford to replace them with high flow models if they plug up or restrict performance. I definitely agree with you guys about clean air being nice, but sometimes you just gotta do what you gotta do .

98_1LE

OK, we all agree that removing the cat is bad for the environment. I'm installing a car sounds 3" inch cat. So anyone have dyno numbers for the exhaust through the muffler?

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87 Formula 350 13.94@96.67
98 Z28 1LE 13.15@107.59
1LE Owners Association

Raymond 5.7 89 Formula

According to Lingenfelter if you have a good cat you lose only 4 to 5 horsepower at top end.

Kevin91Z

iTrader: (1)

I think you'd be over 100 MPH in the 1/4 if you switched the exhaust like you said.

The ODB

I've got news for you all. My friend shawn had one of those 3" high-flow cats and it killed over 100hp. He hollowed it out and gained more than 10 MPH recorded vericom trap speed. He was then running low 12's after that.
questions, feel free to email him about it.
sbeach@postnet.com

ODB

oh as far as the clean air.. forget it. The air is already ruined. I've been overseas a dozen times and have seen how other countries control their own emissions (not) and therefor feel no guilt about releiving some stress on my performance cars. If I were truly dedicated to clean air then I'd stick to a bicycle.

JETHROIROC

I must agree that I find it hard to believe that a high performance cat only takes away 4 or 5 horsepower over a straight pipe. Sounds like some kind of EPA conspiracy to me. Maybe on some four cylinder, mickey-mouse 1.2 liter ***** but not on a real engine pushing out 300+ HP. I've been debating removing my 10 year old stock cats for some time now...in light of ODB's revelation, my sawzall comes out first thing tomorrow!

98_1LE

My old '97 Z28 didn't pick up .1 second ET with the cats removed. I don' beleive that a good modern cat costs more than 10 hp. I have to pass annual inspection so it's it must-have anyway.

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87 Formula 350 13.94@96.67
98 Z28 1LE 13.15@107.59
1LE Owners Association

smithtc

iTrader: (5)

Concerning catalytic converters:

If you can, cut them out. If not, buy aftermarket if your car has extensive mods.

Why? I am an engineer, who had to study this ridiculous crap in classes where people discussed fuel cells, electric power, and other alternate means of transportation. The cats were intended to do away with leaded gasoline. You can past most emission tests without a catalytic converter. If it is old, or your car has many miles, it can cause more harm than good in some cases. I love clean, fresh air. I'd breathe the air out of my no cat exhaust pipe before living in some of our major industrial cities.



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Gunmetal 89GTA T-Tops L98
700R4 with 3.27 gears, street tires
Best 60 ft: 1.996
Best 1/8th mile: 9.02 @ 76.5mph with 60' time of 2.14
Mods: air filter, hypertech chip, 3" exhaust
Current Mods: 8.8wires, cap, rotor, +4 plugs, MAF screens
Servo

IROCZTWENTYGR8

iTrader: (1)

ODB,

A High Flow converter might have taken about 100HP from that dudes car, but if it was a stock converter, it would have taken more.

Some can't take off their converter because of emmissions. So if u can't, its better to go with a High Flow because it still restricts less than a stock converter.

How much HP and Torque does that car make?? What kind of converter was it??

I might E-Mail the dude, but if u know the answers, it would be nicer.

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Looking For:

87 IROC-Z 350 TPI
84 TRANS AM 305 H.O.

[This message has been edited by IROCZTWENTYGR8 (edited March 09, 2001).]

theformula

dont worry about the cat. Your best bet is to pick up some cut outs for $50. That way you can run them at the track, then drive home legal

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91 Formula
305 TPI 5speed
1LE/G92/WS6

Paxton SN92 polished kit, SLP airfoil, ported/polished plenum, March pulleys, Crane AFPR(43psi),Crane Gold 1.6rrs,MSD coil,MSD6AL (5200rpm limit),Holley 9mm wires,Ac delco R43ts plugs,stock chip,Ford SVO 24# injectors,Bosch O2sensor,SLP 1 5/8" headers,SLP catback,shortened shifter,3:73s w/Auburn posi,170* t-stat,JET 195* fan switch, Macewen white face gauges, Autometer gauges, Zoom hi-performance clutch.

IROCZTWENTYGR8

iTrader: (1)

Thats what I am going to do when I get the IROC 350. Its a much better way when u have emmissions and stuff.

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Looking For:

87 IROC-Z 350 TPI
84 TRANS AM 305 H.O.

[This message has been edited by IROCZTWENTYGR8 (edited March 10, 2001).]

91RedBigFinZ

According to random technology, their cats lost a few horsepower at the top end vs having no cat. What i found interesting was the actual gain of about 10ft-lbs torque with a converter. I think the gain of 10ft-lbs torque is better than getting 2 horsepower (and losing torque). Go with the high flow.

The ODB

setting up a dyno test to make a converter look good would be really easy.. just run the engine too lean. The converter will richen up the engine and increase torque.

I think Shawns converter may have been from Random, but I'm still waiting to hear from him on that. I will post it when he tells me.

ODB

The ODB

here is Shawn's reply, I just got it.

"Thrust 3" by 3" high flow. it cost $100. I now why my car lost so much
from
it. I had iron heads on the car at the time at had to run rich just to
keep
it from knocking. I believe a car running rich like that will lose a
****
load more compared to a car running lean. The car would spark knock
when i
put that ****ing thing on and ran 220 deg campared to 160."


ODB

He was making over 350hp at the rear wheels with that engine.