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Discussion Starter #1
1st off, I don't want to make this post on the exhaust sticky, since this is just a downpipe thread.

Real cynicalism..

I still have stock exhaust and main (leaking) catalyst, but just had the HKS downpipe fitted to stock turbo. Quite disapointed considering the hype some people have been giving to this upgrade. "Gain 20 HP!", "MUCH faster turbo spool" etc :)

Spool time is the same, no response until 2500 RPM at WOT.
Low end power is seriously affected. 50-70 MPH in 5th is around a whole second slower, (8.5 vs 7.5 seconds) and you see some real struggling between 60-70 MPH in 5th. That means 150 HP compacts/hatch backs can keep up with me in 5th, which is quite embarassing.

I think I gained 1 PSI according to the stock boost guage. But again, I got nothing to prove that I gained anything at all. Dynos are too inaccurate, with stupid correction factors that can vary between 15% - 30%.

No, no no, there are no vacuum or boost leaks, TPS tested and gives resistance figures within manufacturer tolerances at WOT. Timing is set at default (12 BTDC).
 

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A Happy Dad
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get rid of that stock exh., you could have the biggest dp in the world and not notice a diff with the stock exhaust still on.
 
T

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mdr40z said:
get rid of that stock exh., you could have the biggest dp in the world and not notice a diff with the stock exhaust still on.
:agreed:
 

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Yeah, I think people who feel the 20hp gains with the downpipe are the ones who already had the cat-back. And they probably felt like you do thinking "all this money for nothing" when they first put on their cat-backs
 

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wastegate hose is pulled
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Wow. You actually lost low end torque? I think there is something wrong with your car. Seriously. I did a uppipe and downpipe on my other car and noticed a nice improvement with the OE cat back. Maybe it's that second cat. Dump that, if that doesn't do it then it is time for a cat back. Should be 3" turbo to tailpipe.
 

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Canada, Eh?
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take off your cat and catback, run an open downpipe. if laws are strict, just run around the block, you'll notice a HUGE difference in response...
 

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Anh said:
<snip> But again, I got nothing to prove that I gained anything at all. Dynos are too inaccurate, with stupid correction factors that can vary between 15% - 30%. <snip>
:rolleyes: Too inaccurate?! Puhlease.

If you had a bannana shoved in the tailpipe and replaced the piping ahead of it would you expect more flow? Dump the rest of the exhaust!
 

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TO4R
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downpipe doesnt really do nothing but once you put on a exhaust on you can feel some difference and sound meaner and thats 20 hp gain.
 

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Discussion Starter #10
Re: Re: Cynical post, HKS 3inch downpipe installed

BLKMGK said:
:rolleyes: Too inaccurate?! Puhlease.

If you had a bannana shoved in the tailpipe and replaced the piping ahead of it would you expect more flow? Dump the rest of the exhaust!

Yes, just throw money into the problem.

My car was QUICKER with the stock exhaust and stock downpipe. The exhaust was leaky then as it is now, so that is no excuse.

Comparing the stock exhaust to a tailpipe congested with banana is simply ignorant.
 

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Republican
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OK, wouldent this go in the Shops and parts reviews? But I digress, I put the Dp on my car, and noticed a HUGE differance. you cant put a 3 inch DP on a car with your stock turbo exhaust, and expect a large increase.
 

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AKA Muddy
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You obviously know everything about making a turbo car fast, so why don't you just sell the supra and buy a fast car like a ford ka?
 

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Can't touch this!
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I don't mean to be an ass but yeah think about it for a second.

You can puch all the air you want through a bigger dp but it stillhas to cramm into the stock piping!!!

You should hardly gain anything from this dp unless you make the rest of the piping 3"!

Jason
 

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Premium Member
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ru sure you installed the donwpipe correctly? You could have installed a gasget badly and its blocking the exhaust flow??

Anyways, you should feel an improvement with the stock exhaust and cat... I'm pretty sure you fucked up something or somethings wrong with your car.. try to see if you ECU throws any codes?

Krister
 

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Discussion Starter #16
No gasket between the downpipe and turbo elbow, they used some sealant instead. They broke a stud too.

Anyway, I probably gained 0.5 - 1 PSI with the new downpipe, but torque from 1500 RPM + seems to have dropped or no gain at all.

Ok, took the Supra out for a long drive. 3.5 gallons of 98 octane unleaded and I was ready to test her out. Turbo lag as bad as it has always been, which is the biggest disapointment since people rave on about how aftermarket downpipes cut down lag.

I'm just being realistic here, based on real experience. Of course for 50-70 MPH, I would use 3rd for best performance, but 5th gear is a good way to experience how much low end power there is. Best time I got out of several attempts was 7.3 seconds. A stock 300 ZX TT falls between 7 - 8 seconds, so its not all that bad.

I'm getting a Blitz NUR spec in 2 weeks, hopefully remove the remaining cat, maybe then I will gain 2 Psi over stock, and a hopefully 20 HP increase over stock.

15 - 20 crank HP gain, tops. I dont trust chassis dynos that claim 40 HP gains, I've seen way too many poorly run cars, inconsistent readings and correction factors that don't add up in the real world.
 

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Canada, Eh?
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you dont seem to get it... of course there arent going to be gains with just a DP and a stock cat and catback. judge the mod once you have your NUR spec on the car.
 

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I agree with the others, you won't see much, if any, improvement with just a downpipe.

I installed a 3" cat-back first and barely noticed a difference at all. I was severely disappointed. Then I installed a Defcon downpipe (replaces stock downpipe and the turbo elbow) and I retained one catyletic converter. The car was considerably quicker with this setup. I think I easily picked up 30 hp over stock, maybe even more.
 
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cynicism....cynicalism isn't a word, :)
and also....what size is your DP, and what size is your exhaust?
If the two differ, the downpip is all but pointless, unless your exhaust is bigger, which I doubt.
Imagine it like a river flowing through a twisty valley and then into a dammed lake with only a trickle getting out. Then remove the twisty valley....there is still only a trickle getting out. Such is your exhaust.
 

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I didn't gain any boost increase when I installed my Defcon downpipe , 3" test pipe and HKS super drager. I have to shim my wastegate to increase the boost. With my Profec B the boost shoot up real fast.
 
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