https://www.grcorollaforum.com/threads/top-starter-performance-mods-non-suspension.6775/?post_id=143171#post-143171

post #4

 

To be a little more specific…

I also want to add a downpipe. I have added the Eventuri intake, and CSF Intercooler. I do not want a crazy loud set up and drone is something I’m looking to decrease. I do plan to tune after, but have not fully committed myself!🧐
So, here are some of the things I’m looking into, but searching the exhaust thread is not pretty!
1. I like the limit+1 downpipe as well as the OTL one. I’d like to run a resonator on the midpipe, so I’m leaning towards OTL, so I can pair it myself with a catback that includes a resonated midpipe, or keep the stock midpipe and exhaust.
2. Does keeping the stock exhaust valve function, cause any back pressure issues if running a high flow downpipe?
3. I like the Lachute catback, which can either keep the valve function OEM, or has the ability to have a manually controlled valve. The remark quad tip is another that looks and sounds the part. Lastly, the Apexi quad tip with a downpipe might give me just enough growl when pushing it, yet is somewhat tame, when cruising.

HELP!!

I need some more info and opinions of those who have done it, are doing it, or have some answers to help push me forward!

Thanks for reading!!

Owen

 

To me they are totally worth it and I am giving my opinion based on the many turbo cars that I bolted on aftermarket downpipes, mostly catless except the Cobbs ones which the cat was a HFC and it was placed 3-4 feet down the stream mating with the catback.
What I experienced in all my turbo cars after replacing the downpipes (cat or carless) was a much better turbo response with less turbolag, quicker reving, more boost, more noticeable torque and more HP as well(all of the above).
Unfortunately you can also run into over boosting, lean AFR's and off course CEL. From what I am gathering as of today many tuners wouldn't mess with emissions. If you opt for a decent quality catted HFC you will probably benefit from faster spool up/more HP/tq but it will cost you more. I am sure the tune can somehow control the wastegate and tame the situation a little bit.

 

Almost all turbo cars benefit decently from a downpipe (like literally all of them I've owned have gained at least 15-20whp/tq, the things you mentioned, and didn't cost a ton); the GRC is an exception however, and it's a fairly objective thing IMO, but I cover it in the linked post above.

 

As far as I understand, the turbine of the stock turbo becomes a restriction long before the downpipe. Ditto for the stock valve train at high boost, high RPMs.

Now, if you were running an aftermarket turbo then it would make far more sense

 

I appreciate all of the responses. I understand what a downpipe does and clearly wasn’t as specific as I needed to be I guess. I’m not looking to max the turbo, but simply add a bit to what is already there with a tune that tapers boost up high, but adds some more low and mid range response. I think somewhere in the range of 300-310 to the wheels, but it’s not about numbers. It’s about drivability.
That is where my exhaust questions are coming from. Truth, I don’t mind spending a few extra dollars to ensure a free flowing exhaust, that is helping keep the motor safe related to back pressure. At the same time, I am not looking to add a downpipe if it’s not a restriction for my goals.
I hope this makes sense.

 

Intake and 92/93 Ecutek tune and you'll be right at 300-310whp. FMIC is a bonus if you dont want to lose power due to heatsoak/pulled timing.