Getting an LS1 Down to the numbers

[for2n8son]

I am running an LS1 in a 2002 Camaro and I'm having trouble getting the HP down without losing all my torque in the process and/or leaning it out so badly at high RPM's that I burn a piston. Are there any LS1 runners that have solved the problem?

[Adam Ginsberg]

The LS1 cars in CA use a restrictor plate to bring down their numbers. The biggest complaint is poor/less than desirable throttle response, but not running lean unless you're making changes to the tune in some way (say, via LS1Edit).

[for2n8son]

I was told you could get some of the torque back working with the exhaust.

Any idea on what to do there?

[ls168camaro]

Al,

 

Welcome to the group. Try a search on here to find a few threads about restricting an LS1.

How have you tried restricting yours so far? What are the results and what does it do uncorked?

I had some plastic restrictors made that insert in the bellows between the maf and the throttle body. They are in my car and 2 others with zero issues so far. Most of us run a 46 mm plate.

Yes, the biggest issue is killing the torque to get below the hp number. Which I have been wanting to experiment with some different exhuast setups. What kind of exhuast are you running.

Let me know how I can help in anyway.

Bryan

[Glenn]

Loss of TQ due to a restrictor is common. The LT1's in CMC (230 HP) make peak TQ at about 2K-2.2K. I can bet your isnt as bad.

As for the AFR...... well that tells me your playing w/ the tune or you have an issue w/ the car. PCM mods are not legal in any way.

 

Small exhaust size will help the TQ.

[ls168camaro]

The real problem is the LS1 makes similar hp and tq. The tables are based upon the older motors which made much more tq than hp. If you want to only talk peak the avg LT1 in CMC or CMC2 will have a higher peak tq number than an LS1. Albeit, at a lower rpm.

 

His AFR could be off due to an air leak as well. How have you had it restricted?

 

I believe one of my issues is my exhuast which has cats but they maybe aftermarket or higher flowing. Then custom larger diameter Y pipe into custom 3" straight pipe out the back. I'm looking to try a factory Y pipe/exhaust, or a smaller than current diameter Y pipe without cats, and 2.5" exhaust with or without a muffler.

 

I would like to hear from the California LS1 cars and how they are restricting them.

[for2n8son]

Thanks for the help, guys. The first dyno session was just to get a baseline and to try to figure out how much needed to be done. We didn't even run a sheet at that time. I don't remember exactly what the numbers were, but it was noticeably over 300. We were tryng to restrict airflow in front of the maf with duct tape when it leaned out on us. I don't think the tuner had done anything to the computer.

Afterward, I had an odd assortment of restrictor plates which I got from a friend. The smallest one would jam the butterfly, so I tried the next largest one. Results, 305 HP. Someone mentioned the 46mm size, so I have someone working on one for me and a spacer to take care of clearance.

Thing is, I wasn't running from anyone on the straights, I wonder if it is going to be competitive when I get under the HP limit. Just out of curiosity, can I run an LT1 in a Gen4 that came with a LS1?

Edited August 2, 2010 by Guest

[for2n8son]

P.S. I'm running 2.5" true duals with gutted cats and an H pipe just before the transmission support.

[Al F.]

Al, if that was a T2 car it probably has had a tune. It would be well worth your while to check, as easy as swapping boxes with someone you know hasnt monkeyed with it. More restrictive exhaust will certainly help maintain the torque.

[for2n8son]

Thanks Al. Can you swap engine types in the same generation? I.E., can I run the LT1?

[Glenn]

Al's right, if its a T2 car, its been tuned to w/in an inch of its life.

Also, DO NOT PLACE A RESTRICTOR RIGHT IN FRONT OF THE MAF!!!!!! It will cause massive errors in what the MAF see's as airflow thru it.

 

Place the plate behind it on the front lip of the TB. Then slide the air bellows back on and that will hold it in place.

 

Your duals are hurting you. They are great for peak numbers on LS cars. way to much air flow for a restricted LS1. the OEM exhaust is 2.75" single. You have 2.5" duals. Duals help in high flow conditions. The restrictor works against you in this case. You need to run at most a single 3" pipe after the Y. Run a spiral flow bullet muffler to help keep the backpressure up some.

 

And yes, you can run an LT1 in any year 4th gen, but you will be governed as a LT1 car w/ regards to the rules. Its also 75lbs heavier on the nose.

[for2n8son]

Glenn, thanks for the advice on the exhaust. The restrictor plates I have are flat plates that go behind the TB, between it and the intake manifold. Is that OK or is it better to restrict the flow in front of the throttle body?

[Glenn]

What you have is the required plate for T2. That is where they had to place it. Its OK as long as the hole is large enough to keep the TB blade form hitting it, but at some point it will just like you found. Placing it in front of the TB allows the air to smooth out when entering the intake thanks to the TB blade. It will swirl alot off the back side of the plate. Your location also requires RTV to seal it.

[for2n8son]

So what you are using is a round disc the size of the TB lip with a 46MM hole in it, held in place by the bellows?

[Glenn]

Yep. You can make it out of a nylon cutting board or some delron if your good like that.

[for2n8son]

Well I'll be darn! And here I thought I had this big engineering project in front of me.

[ls168camaro]

Glenn made the first restrictor and we put it in front of the MAF and it wouldn't run right. I think it messed up the flow of the air to much. We got a T2 restrictor that went behind the TB. But like you have experienced if you get too small like we need to make the number it will hit the TB blade. I also think this can cause a problem with disturbing the airflow. I agree with Glenn that the blade smooths the air out better.

 

We went to a machine shop and they ordered a stick of plastic. They cut them into thin discs, machined the outside so that it fits snug in the bellows, and then cut different diameter holes. They were sized according to the bellows and not the TB. They fit so snug in the bellows that you usually need a flatblade to get them out. Also, had them make some with the holes offset so you could turn it a certain way in the bellow. Can't remember without looking at all my dyno's what the result was or if it mattered any. They also engraved the size.

Get with me and we can get them to make you a good assortment if you want.

 

I have also heard some say that the gutted cats can be an issue.

You should also get your computer checked for a tune. Mine was a T2 car and I got 2 computers with it. The tuned computer was definitely aggressive and hurt the motor.

 

I ran CMC2 in my LS1 the first year that we could run 280 hp. What I have learned is that the LS1 makes such a high peak hp number that you really have to squeeze it down alot. This peak number really doesn't help much because the curve isn't that flat. So anything you can do to cut down on that high rpm peak should help you run a bigger restrictor. I'm thinking exhuast would be key here.

 

Do you have an LS6 intake? That could hurt you. Do you run an stock airbox or aftermarket lid? I have tested alot with both and I run the aftermarket lid.

[for2n8son]

Bryan,

 

As I understand it, you have to have the stock intake in T2 and I haven't done anything to it. I assume it's stock. I'll have to confess I don't know how to distinguish between them. I do have a stock airbox. Which aftermarket lid has worked the best for you?

After this weekend I'm going to try some stuff with the exhaust and see what happens.

[Glenn]

All '02 and most '01's came stock w/ the LS6 intake. Its worth a few buck ($200) and you will likely get an LS1 intake (98-00) in trade for no additional cost.

[for2n8son]

I am now the proud owner of a round plastic disc with a 46mm hole in it. By this evening it will be firmly wedged in my intake system. I notice that the throttle plate is a little offset. Does it make any difference if the hole in the restrictor isn't offset to match it?

 

Thanks for the tip on the intake. That will probably have to wait until after Road Atlanta this weekend.

[ls168camaro]

I had an LS6 and sold it on LS1tech for $300. I think the only way you can tell is pulling the intake.

http://www.ls1howto.com/index.php?article=5

 

I don't think it makes a difference who makes the aftermarket lid. To me the most important thing is how well it fits.

 

Are you putting it in front of the TB? I had some made that were offset but can't pull up my dyno's to review as I can't remember the results. My thought was putting the hole up or down depending on the airpath through the TB. That is fine tuning but I think anyway you put it in should be fine as long as its near the middle. Machine shop didn't want to offset too much and make the plate breakable.

[for2n8son]

I do have it in front of the throttle body. Man, that's a small hole. I was having trouble breathing just looking at it. I hope to get a dyno run before I go to Atlanta. I'll shared the numbers if I get it done.

[rleng11548534736]

I run a 2000 LS1 with a 46mm restrictor plate that BryanL gave me. Ran CMC2 numbers of 260hp/298tq.

Pretty good numbers, but no noise. sounds like at volt or something. would be interested in seeing your results of your y-pipe and exhaust setup. i will be doing something in the off-season.

Be sure to run the motor a qt over fill mark on the oil.

[for2n8son]

I have been running a half quart over. I'll add the other half. I would be happy with your numbers, especially the torque. Everybody around here seems to really push the edge of the chart.

[Al F.]

Excellent sharing of tech guys, keep it up.