I lost the horsepower on my 3kgt!! Help!

[HKmitsubishiman]

Hi people, if you read my thread about my spin out, you probably know why I did what I did. Yesterday, I changed a lot of things in one freaking day on my 93 3000gt base model. I changed: muffler, springs, rims. First thing I did was the muffler, I fxxked up my muffler from spin out, so I decided to cut the whole thing and put a single muffler on the left side only, since the stock muffler is on the left side, and the tips on the right side are just from the same muffler, my new muffler is 4.5" inch tip, I got it from my friend, and it has no brand. Second, I lowered my car with Ground Control adjustable springs, which I don't think will affect my horsepower. And lastly, I change the rims to 17s. My stock rims are 16s, and stock tire size is 225/55/16. The new rims I got, have tire size 225/55/17. So the new rims, with the tires, are simply 1 inch bigger. I think it will affect the power a little. When I drove my car after everything was done yesterday, GOD!! My car is freak damn slower like mofo. First, I couldn't feel no force when I accelerate. Second, when I look at the speedometer as I accelerate, god, I feel like my car is as slow as the Mirage I have. Third, I have to freaking floor the gas when I go up the hill.

So!! People, please help, what do you think my problem is? Rims or muffler? Or other things? I really can't admit that my 3kgt is so slow.

[Musashi3000GT]

Such a big muffler? dude I think you lost backpressure. I remember when I changed my mufflers I felt absolutely no power at all at bottom end, I was sooooo pissed off cause the car got real slow, turns out the shop had put a 3inch piping all the way through instead of the 2.5 I asked for. then even that was slow so I opped for a 2 1/4 inch and its still slower than stock. and my tips are only 3 inch. so if you messed up on the muffler/ pipe you will loose alot of power.

[Hotshot8792]

check your throttle cable and your throttle position sensor and make sure they didnt get messed with during the accident, or else you could be having the throttle all the way to the ground but only getting 50% throttle.

[youngmanvr4]

Plus sizing your wheel & tire combination was designed to enhance vehicle performance and looks by allowing fitment of larger diameter rims and lower profile tires. The theory is that while making these changes, you keep the overall tire diameter within 3% of the original equipment tires. This is important because larger variances can cause problems with transmission shift points which can decrease fuel mileage. It can also confuse braking system computers which can even lead to brake failure.

Here's the rule of thumb for "plus sizing":

Plus 1:
Increase section width by 10mm
Decrease aspect ratio by 10 points
Increase rim diameter by 1 inch

Plus 2:
Increase section width by 20mm
Decrease aspect ratio by 20 points
Increase rim diameter by 2 inches.

That also could have something to do with your power loss going up a hill because in could have done something to your transmission. But what do i know?

[HKmitsubishiman]

Oh, I'm probably changing the tires to 225/50/17. That would help I think. And the muffler, do yall think stock muffler is a good choice? I kinda feel that my car is slow because of the muffler. And I don't want to spend much money on aftermarket exhaust. So stock??

[HKmitsubishiman]

And the throttle, I don't think I messed it up, because my back hit the wall, and it wasn't a hard hit. I drove away from the scene quickly too, haha. And I felt the same, so I think my car was good after the accident, and b4 I changed the things.

[Musashi3000GT]

Its totally the exhaust, as soon as you change it you will see, and yes stock is the cheapest way to go (and most effective) or a borla cat back for about $500.00 I dont know! ask around and you'll find alot of dirrect fit aftermarkets.

[HKmitsubishiman]

Thanks musashi! I'll probably go with stock, cuz I'm kinda broke now, and I dont want my parents to kill me. I'm the kind of person that want to show off, haha sorry. So is there anyway I can make the exhaust sound louder with the stock muffler? I just ordered a test pipe, didn't receive it yet. Do you think it will make the stock muffler louder? And will it make the car quicker?

[youngmanvr4]

Dont take my word for it but removing the cat (getting a testpipe) will make flames come out of your pipes. I dont know if thats true or not. I'm not sure how much louder it will make it but i'm sure it should do something. I dont that if you gut your cats it will make it louder...so i would think it would do somewhat the same. Quicker...i have you clue on. I think it will be the same as turning off your AC. Help to free up some HP but you wont feel 5 hp. Plus if you dont again any torque then you will feel no differents because you dont feel hp. You only feel torque. Why am i giving a math class when you already know about that? I could teach you alot about it if you dont know anything about hp and torque.

[HKmitsubishiman]

I think it's true that putting a test pipe will make the car back fire. But not sure if the stock muffler can back fire. And the thing that I worry the most is, will the test pipe hurt or damage the engine?

[youngmanvr4]

I have never herd of it hurting your engine. I'm going to get a test pipe for my VR-4 when i get it. So i see not problems that i know of. I could damage or make the paint come off of somehouse's in your town if everyone had tests pipes on they're cars.

[RX_speed]

i dont know alot about SLs but if your car relies on backpressure that much, then gutting or removing your cat may cause a loss of power too

[Musashi3000GT]

Here is a testament from someone who has already been there: I have a 94 SL. I put a custom made cat-back system on my car with two CF mufflers. from the cat back to right before the gas tank it is 2.5 inches. then there is a "Y" pipe to split the two rear mufflers. the two splits are 2 1/4 inch. this set up made me loose low end power. this means my car feels really dead and slow untill I hit about 3000rpm. up around 6000rpm I gain like 6 HP. then I installed a test pipe, I lost power up until around 3600-3800 rpm. I did gain like 4 more HP up around 6000rpms. So how many times a day do you drive at constants of 6000 rpms? In other words without a turbo or a Supercharger there is no need for a wide exhaust and a test pipe! that is why only GT cars do these mods, they ride 6000-7000 rpms all day! back pressure is a real tricky bitch!

[RX_speed]

cool, so i was right

[azn3000GTRacer]

why ddint u go 245/45/17 instead? u would of got less tire and would save on weight