so i got my megan racing downpipe installed today at a tuning shop in md (ams tuning with their evo viii package deal, being the walbro fuel pump, hallman pro manual boost controller, and defi d-series boost gauge... great deal on parts and labor, thanks alot mike and cory >;])

anyway, after turning up the boost to 20 psi, my car feels like it pulls a hell of alot less than it used to when i had my stock downpipe on and no boost controller.... what the hell?!?! i guess it could be a buncha things, but here's some things i noticed:

rattling of the downpipe after i let off WOT above probly 3000rpm... in other words, if i floor it past 3k rpm and let off the gas completely, i hear the downpipe rattle under me...

also, the turbo definately sounds a little bit different.. not sure if this is cause of all the modding of the hoses and the such so it makes it sound a little bit off, but either way, that's pretty much all i can gather from my situation.

so.... help? anyone have any idea what the problem could be? i know ams has done these installs billions upon billions of times so i dont kno what the problem is exactly.. anyway, any input given is GREATLY appreciated >;] sorry for the long post.. thanks

--Jonathan

o ya, and i also have an Ultimate Racing cat delete with an HKS 30th anniversary hi power catback exhaust... making it a 3" turboback, finally >;] sux tho that there's probly a leak somewhere sigh

 

i am guessing boost leak or you didnt get it tuned

 

did you tune it?

 

A little bit of rattling is not entirely unusual, although it probable wouldn't hurt to jack your car up and check the bolts on the downpipe and exhaust anyways.

My only questions for you are what kind of boost readings are you getting and is your turbo spooling up faster or slower than it did before??

 

The rattling could be the lower frame tie bars hitting the downpipe. Also you may have boost leaks and you might be running too rich due to the new high flowing fuel pump

 

why don't you take it back to AMS and ask them??

 

sounds like you didn't get a tune & u had a crappy install. this is why i do my own work...

 

with the mbc, you're boost is not going to peak as much.

However, with the tune, you get a smoother transition on the AFR, and better pull on top end, which feels slow...


here is a recap : no more 23psi boost peak at 3500 rpm + smoother AFR ratio across the power band + constant boost level = it feels like it's slow.

But you shoud really go check out your times at the track to be sure.

 

maybe lost 2 much backpressure so you dont have the low end tq

 

i didn't get it tuned, but virtually all the people that i talked to that have these few mods said they experienced an extreme improvement in performance, etc.... im pretty sure it's not that i just think it's goin slower cause i have a pretty good memory as to how fast i could fly through my gears and watch the mph go up, and it's not even comparable now as to how it used to be...

i already checked, and theyre wayyy above them, over an inch or maybe even more, so they clear it by far. as far as the fuel pump i kno alotta other people runnin this pump and it wasnt an issue.... altho i guess i could be that select few that gets f**cked randomly

the boost seems like it's goin up faster as far as what the gauge says, and i hit up to around 19-20 psi, but as far as response from the car as if im really hitting boost that high? no way.

seems probable.. but for some reason i still feel like this is way too much power that would be lost from an issue like this, especially because of all the research ive done on other people having their evos modded in a similar way...

already done.... called them and they said theyd be glad to take a test drive around and feel how the car is now... in ne case, ill keep the status posted as to what the status is right now... but if anyone has faced a similar issue or may just have some advice or something, PLEASE let me know, im all ears!

--Jonathan

 

I have a hard time telling differences in acceleration and boost curves by the seat of my pants, so I have an accelerometer. I too, installed a MBC and found that, although it pulled harder up top (and increased the peak HP from 270 to 295 at 22 psi), it FELT slower. The accelerometer confirmed that I lost 0.07 Gs of peak acceleration (0.64 vs. 0.71) in first gear with no launch. However, looking at the horsepower curves, the area under the curve is much broader.

I noticed at the Autocross that wheelspin exiting tight corners was gone, but the car felt less responsive, so I took off the MBC. It also put me back in A Stock, where I don't have to compete with those on Hoosiers.

On the downpipe issue, David Buschur posted an excellent series of articles in which he found that opening up the exhaust upstream did not help if you don't open it downstream. His tuning theory is to remove restrictions starting at the exhaust and moving forward.

If you think about it, the best exhaust for a turbo would be a megaphone; one that gets larger as it goes toward the tip, to allow the gases to expand and accelerate as they go. A larger downpipe is going to help very little if the stock exhaust is left in place.

I bet your car IS faster, but I have no doubt it feels slower with the mods that you did.

 

1. rattle is usual and more common than most think---touching the oil pan or cross bars
2. my thing is to always use gasket seal beause most of the seals that come with new exhaust pieces are cheap and leak all the time
3. i am sure if youlift the car and push the dp to one side it is touching the oil pan---hence your rattle
4. hey guess what with a dp,cat delete,cat back-----your exhaust is increased which means more work for the turbo<pressure> which is why it is louder

my2cents

take it back to them and let them get it right!
This was done by Atlantic Motor Sports

 

the reason why it feels slower is because you did a downpipe and mbc at the same time. The downpipe makes it harder to build boost at lower rpm. You lose some torque with the mbc because an ebc can open the wastegate fully until you hit the desired boost and then it closes to that actual level where as a mbc is always at that level. The car should feel slower in 1st/2nd, but smoother but you should notice hella difference in 3rd +. I would say get a flash and that will help you out.

 

[QUOTE=plokivos]However, with the tune, you get a smoother transition on the AFR, and better pull on top end, which feels slow...QUOTE]

Would you say that getting a flash (on an otherwise stock evo) makes the car FEEL slower?

 

Well, if you hear a rattling when you let off from WOT, your DP is probably rattling when you're at WOT. You just won't hear it over the engine noise.

If it is rattling, there's a good chance that it's setting off the knock sensor, which in turn will pull timing. Pulled timing= less HP.

Fix the rattle first.