Low Mile Per Hour after LT install
Thread Starter
Staging Lane
Joined: Jan 2024
Posts: 79
Likes: 21
From: Cape Coral
Low Mile Per Hour after LT install Hey all,
I recently installed American racing LT's with catted Y pipe and a 25% underdrive crank pulley. It felt very "laggy" for a while but now it seems to be quicker, I'm assuming the ECU is learning. I don't have a track near me so I've been using Draggy since I bought the car.
Here's where I'm confused, I've read on the forms for a while now that it seems most gained 2-3 (or more), MPH after a long tube header install. My previous run was a 13.5 at 103 MPH with just the Borla cat back, (that came on the car), and Volant cold air kit. Now, with those same mods plus LT's and the underdrive pulley, Draggy tells me I'm running 13.3 at 104 MPH.
I'm I wrong in thinking that the mile an hour is low for this modification?
Thanks
I recently installed American racing LT's with catted Y pipe and a 25% underdrive crank pulley. It felt very "laggy" for a while but now it seems to be quicker, I'm assuming the ECU is learning. I don't have a track near me so I've been using Draggy since I bought the car.
Here's where I'm confused, I've read on the forms for a while now that it seems most gained 2-3 (or more), MPH after a long tube header install. My previous run was a 13.5 at 103 MPH with just the Borla cat back, (that came on the car), and Volant cold air kit. Now, with those same mods plus LT's and the underdrive pulley, Draggy tells me I'm running 13.3 at 104 MPH.
I'm I wrong in thinking that the mile an hour is low for this modification?
Thanks
TECH Fanatic
Joined: Jan 2022
Posts: 1,362
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I’m too new to know for sure but I bet that is somewhere in the ballpark of being correct. I bet the headers were/are good for 10-15 horsepower untuned and maybe a little more tuned. As for the under drive pulley it’s probably negligible.
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Joined: Jul 2009
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Hey all,
I recently installed American racing LT's with catted Y pipe and a 25% underdrive crank pulley. It felt very "laggy" for a while but now it seems to be quicker, I'm assuming the ECU is learning. I don't have a track near me so I've been using Draggy since I bought the car.
Here's where I'm confused, I've read on the forms for a while now that it seems most gained 2-3 (or more), MPH after a long tube header install. My previous run was a 13.5 at 103 MPH with just the Borla cat back, (that came on the car), and Volant cold air kit. Now, with those same mods plus LT's and the underdrive pulley, Draggy tells me I'm running 13.3 at 104 MPH.
I'm I wrong in thinking that the mile an hour is low for this modification?
Thanks
I recently installed American racing LT's with catted Y pipe and a 25% underdrive crank pulley. It felt very "laggy" for a while but now it seems to be quicker, I'm assuming the ECU is learning. I don't have a track near me so I've been using Draggy since I bought the car.
Here's where I'm confused, I've read on the forms for a while now that it seems most gained 2-3 (or more), MPH after a long tube header install. My previous run was a 13.5 at 103 MPH with just the Borla cat back, (that came on the car), and Volant cold air kit. Now, with those same mods plus LT's and the underdrive pulley, Draggy tells me I'm running 13.3 at 104 MPH.
I'm I wrong in thinking that the mile an hour is low for this modification?
Thanks
Joined: Nov 2001
Posts: 34,643
Likes: 2,571
From: Schiller Park, ILL Member: #317
You won't see full gains from the LTs until it's tuned, and the cats will hold back a few HP as well. With tuning, ~20+ rwhp gain can be expected from LTs with ORY (assuming there's already a cutout or good flowing muffler/catback). If the car has completely stock tuning, then the gains might be a bit more as there is something left on the table even with a totally stock car.
12 Second Club
Joined: Apr 2015
Posts: 154
Likes: 37
From: West Coast
Most do gain around 3-5 mph.
I picked up about 4.5mph many years ago when I had the stock ls1 with LTs. That was untuned as well.
From what I remember when I put mine on, there was a big difference from around 3k rpm on up compared to stock.
I don’t have any experience with the draggy app. (not sure how accurate it is)
FWIW… I would say it’s not going to be as accurate as a time slip from a drag strip though.
I picked up about 4.5mph many years ago when I had the stock ls1 with LTs. That was untuned as well.
From what I remember when I put mine on, there was a big difference from around 3k rpm on up compared to stock.
I don’t have any experience with the draggy app. (not sure how accurate it is)
FWIW… I would say it’s not going to be as accurate as a time slip from a drag strip though.
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Thread Starter
Staging Lane
Joined: Jan 2024
Posts: 79
Likes: 21
From: Cape Coral
You won't see full gains from the LTs until it's tuned, and the cats will hold back a few HP as well. With tuning, ~20+ rwhp gain can be expected from LTs with ORY (assuming there's already a cutout or good flowing muffler/catback). If the car has completely stock tuning, then the gains might be a bit more as there is something left on the table even with a totally stock car.
Unless I've been misreading and they had to get tuned as well. Are the 98's factory tunes that different?
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Staging Lane
Joined: Jan 2024
Posts: 79
Likes: 21
From: Cape Coral
Most do gain around 3-5 mph.
I picked up about 4.5mph many years ago when I had the stock ls1 with LTs. That was untuned as well.
From what I remember when I put mine on, there was a big difference from around 3k rpm on up compared to stock.
I don’t have any experience with the draggy app. (not sure how accurate it is)
FWIW… I would say it’s not going to be as accurate as a time slip from a drag strip though.
I picked up about 4.5mph many years ago when I had the stock ls1 with LTs. That was untuned as well.
From what I remember when I put mine on, there was a big difference from around 3k rpm on up compared to stock.
I don’t have any experience with the draggy app. (not sure how accurate it is)
FWIW… I would say it’s not going to be as accurate as a time slip from a drag strip though.
Right after they were installed the car ran like a pig... I was really disappointed but after driving it around it's livened up a bit. Having said that, it doesn't feel much different in the mid range than it did with the stock exhaust manifolds.
Thread Starter
Staging Lane
Joined: Jan 2024
Posts: 79
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From: Cape Coral
Joined: Nov 2001
Posts: 34,643
Likes: 2,571
From: Schiller Park, ILL Member: #317
Post #5 above is honestly the only time I've ever heard of anyone gaining ~5 mph from an LT header install on an otherwise stock LS1 with stock tuning (assuming the car wasn't running open headers for the 'after' run, and/or a cutout or catback swap wasn't combined with the header install). I wouldn't expect that, assuming same track/same weather/etc. I think 3-4mph with tuning is probably a more realistic expectation - of course, that's speaking of a stock engine (if it already had a cam, etc., then I could certainly see bigger gains being possible). Also you have cats, so that will cost you a couple of HP.
12 Second Club
Joined: Apr 2015
Posts: 154
Likes: 37
From: West Coast
Trap speeds should increase 3-5 mph. I know I was going 109 before LTs and would average 112-114 after, with no other changes besides headers.
LTs with ORY pipe. No cats, dumped before rear axle. My car might be on the lighter side as it is a hardtop with low options. It’s also a 98’. Also a manual car.
I have a thread from around 2015 where I would consistently post updates.
It’s not uncommon, or at least back in the day it wasn’t for “true” bolt on cars to trap around 118+ depending on weight and other factors such as driving, DA, etc.
Uncorking those stock log manifolds, cats and stock Y pipe really does add some horsepower
LTs with ORY pipe. No cats, dumped before rear axle. My car might be on the lighter side as it is a hardtop with low options. It’s also a 98’. Also a manual car.
I have a thread from around 2015 where I would consistently post updates.
It’s not uncommon, or at least back in the day it wasn’t for “true” bolt on cars to trap around 118+ depending on weight and other factors such as driving, DA, etc.
Uncorking those stock log manifolds, cats and stock Y pipe really does add some horsepower
Joined: Nov 2001
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From: Schiller Park, ILL Member: #317
5mph isn't common today, nor was it common 10-20+ years ago, for doing only LT headers with no tuning and absolutely no other changes (such as adding a cutout, dumps, catback, or anything else) to an otherwise stock LS1. 3mph I could see, but not ~5 on average (especially not for someone still using cats like the OP). If you removed the entire factory system from the cylinder heads to the rear bumper and did LTs with dumps all at once, then maybe that sort of gain could be expected even with stock tuning.
The fastest true bolt-on cars will absolutely have tuning. Tuning is a "bolt-on".
The fastest true bolt-on cars will absolutely have tuning. Tuning is a "bolt-on".
Thread Starter
Staging Lane
Joined: Jan 2024
Posts: 79
Likes: 21
From: Cape Coral
5mph isn't common today, nor was it common 10-20+ years, ago for doing only LT headers with no tuning and absolutely no other changes (such as adding a cutout, dumps, catback, or anything else) to an otherwise stock LS1. 3mph I could see, but not ~5 on average (especially not for someone still using cats like the OP). If you removed the entire factory system from the cylinder heads to the rear bumper and did LTs with dumps all at once, then maybe that sort of gain could be expected even with stock tuning.
The fastest true bolt-on cars will absolutely have tuning. Tuning is a "bolt-on".
The fastest true bolt-on cars will absolutely have tuning. Tuning is a "bolt-on".
Just so were on the same page. I do have full exhaust on the TA (just not dumped). American racing long tubes with catted Y pipe and a Borla cat back, (came with the car).
I'm not sure if this makes a difference but it dyno'd 301 hp 291 tq at the wheels with the Borla and the volant cold air kit... I'll let you know how it dyno' d and feels on Friday
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Hey RPM,
Just so were on the same page. I do have full exhaust on the TA (just not dumped). American racing long tubes with catted Y pipe and a Borla cat back, (came with the car).
I'm not sure if this makes a difference but it dyno'd 301 hp 291 tq at the wheels with the Borla and the volant cold air kit... I'll let you know how it dyno' d and feels on Friday
Just so were on the same page. I do have full exhaust on the TA (just not dumped). American racing long tubes with catted Y pipe and a Borla cat back, (came with the car).
I'm not sure if this makes a difference but it dyno'd 301 hp 291 tq at the wheels with the Borla and the volant cold air kit... I'll let you know how it dyno' d and feels on Friday
12 Second Club
Joined: Apr 2015
Posts: 154
Likes: 37
From: West Coast
5mph isn't common today, nor was it common 10-20+ years ago, for doing only LT headers with no tuning and absolutely no other changes (such as adding a cutout, dumps, catback, or anything else) to an otherwise stock LS1. 3mph I could see, but not ~5 on average (especially not for someone still using cats like the OP). If you removed the entire factory system from the cylinder heads to the rear bumper and did LTs with dumps all at once, then maybe that sort of gain could be expected even with stock tuning.
The fastest true bolt-on cars will absolutely have tuning. Tuning is a "bolt-on".
The fastest true bolt-on cars will absolutely have tuning. Tuning is a "bolt-on".
Not all setups respond the same. Too many variables. I use to know someone who had a H/C/I FBody trap 115 at the same track.
Way too many variables.
Regardless I’m sure once you get your car tuned it will run much better!
Thread Starter
Staging Lane
Joined: Jan 2024
Posts: 79
Likes: 21
From: Cape Coral
Thats why I mentioned 3-5mph, especially if it’s tuned.
Not all setups respond the same. Too many variables. I use to know someone who had a H/C/I FBody trap 115 at the same track.
Way too many variables.
Regardless I’m sure once you get your car tuned it will run much better!
Not all setups respond the same. Too many variables. I use to know someone who had a H/C/I FBody trap 115 at the same track.
Way too many variables.
Regardless I’m sure once you get your car tuned it will run much better!
Joined: Nov 2001
Posts: 34,643
Likes: 2,571
From: Schiller Park, ILL Member: #317
Without tuning (and especially with cats), I wouldn't even say that 3-5 is common; probably about half that with no other exhaust changes at the same time (and assuming a full exhaust system, not open headers, etc.)
Agreed. I'd say that your gain of 4.5mph untuned was the exception rather than the rule. There are always some setups that respond freakishly, but that's not the norm and folks shouldn't be disappointed if they don't see that.
If you had gone from a 100% factory setup to LTs with ORY and a cutout, or axle dumps, or even a good flowing catback all at once, then I'd say to expect bigger gains. But with just adding catted LTs to an already good flowing catback, the difference won't be quite as dramatic. Tuning will certainly help though.
Agreed. I'd say that your gain of 4.5mph untuned was the exception rather than the rule. There are always some setups that respond freakishly, but that's not the norm and folks shouldn't be disappointed if they don't see that.
If you had gone from a 100% factory setup to LTs with ORY and a cutout, or axle dumps, or even a good flowing catback all at once, then I'd say to expect bigger gains. But with just adding catted LTs to an already good flowing catback, the difference won't be quite as dramatic. Tuning will certainly help though.
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Without tuning (and especially with cats), I wouldn't even say that 3-5 is common; probably about half that with no other exhaust changes at the same time (and assuming a full exhaust system, not open headers, etc.)
Agreed. I'd say that your gain of 4.5mph untuned was the exception rather than the rule. There are always some setups that respond freakishly, but that's not the norm and folks shouldn't be disappointed if they don't see that.
If you had gone from a 100% factory setup to LTs with ORY and a cutout, or axle dumps, or even a good flowing catback all at once, then I'd say to expect bigger gains. But with just adding catted LTs to an already good flowing catback, the difference won't be quite as dramatic. Tuning will certainly help though.
Agreed. I'd say that your gain of 4.5mph untuned was the exception rather than the rule. There are always some setups that respond freakishly, but that's not the norm and folks shouldn't be disappointed if they don't see that.
If you had gone from a 100% factory setup to LTs with ORY and a cutout, or axle dumps, or even a good flowing catback all at once, then I'd say to expect bigger gains. But with just adding catted LTs to an already good flowing catback, the difference won't be quite as dramatic. Tuning will certainly help though.