3.5” exhaust

Speedie6

Speedie6

Silver Member
Greenie N00B Member
Greenie Member
So, I see that Corksport recently introduced a 3.5” exhaust for the MS3. They actually have two options, full 3.5” turbo-back, and a 3.5” downpipe to 3” cat-back option. They claimed to be working on an MS6 version, and CS has continued to support the MS6 platform. But ultimately who knows if they will actually do an MS6 version.

Basically, they claim that while you can run more than 600 HP on a 3” exhaust, when you are in that range of power, you are better off with a 3.5”. They claim that compared to a 3”, a 3.5” will spool a few hundred RPM faster, and hold peak boost longer, when at higher HP levels. Of course they are selling a product, I have no idea how correct their claims are, but, seems conceivable to me.

They are totally into sticking with stock flange (5-bolt) connections from turbo to downpipe. Which isn’t super helpful if you are running something else like a Precision Turbo.

But, their claims just got me thinking if upgrading to a 3.5” exhaust is actually worthwhile. I’ve already spent an absurd fortune on my car, why not spend a little more on a custom 3.5” exhaust? Its only useless money right? (Honestly, I probably won’t, but I figured I might as well learn about it as an option.) My PT6062 only has a 3” exhaust connection, so, I’m not sure a 3.5” downpipe would really gain anything. Though my dump tube connection is fairly close to the turbo and maybe if the downpipe was 3.5” at the merge of the dump tube, that might have some benefit. Or might not.

Just wanting to learn what people think. Thanks.
 
On a turbocharged engine, the best exhaust is the one you can get that's closest to no exhaust at all. For good examples, look at drag racing cars.
 
Speedie6 said:
Would there be any value to going to a 3.5” downpipe given a turbo with a 3” exhaust connection, plus a 44mm wastegate piped into it?
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Simple answer is yes. And to answer your concern that your turbo outlet only has a 3" v-band connection...well that typical and ok.
The turbine wheel exducer (outlet) is only 62mm (2.44inches) but that also doesn't matter in this case. The rate that the exhaust gas can expand and escape the turbine wheel directly relates to overall performance. The ideal turbine outlet will have an expansion "cone" of about 12 degrees off the radius. So 2.44 -> 3.0 -> 3.5 loosely supports this expansion and will help reduce pressure on the turbine outlet which helps spool and peak power.
 
Barett@CorkSport said:
Simple answer is yes. And to answer your concern that your turbo outlet only has a 3" v-band connection...well that typical and ok.
The turbine wheel exducer (outlet) is only 62mm (2.44inches) but that also doesn't matter in this case. The rate that the exhaust gas can expand and escape the turbine wheel directly relates to overall performance. The ideal turbine outlet will have an expansion "cone" of about 12 degrees off the radius. So 2.44 -> 3.0 -> 3.5 loosely supports this expansion and will help reduce pressure on the turbine outlet which helps spool and peak power.
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Any Update on the 3.5 for the speed6 really needing one lol
 
Haedenjames said:
Maxed out on the cst5. only way to make more power per my tuner is a 3.5inch exhaust system. But literally no one makes one
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upload_2023-8-22_15-45-13.png

So, uh, who's your tuner?

Also lol @ GTX71

Edit: How much WHP are you making currently?
 
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Just about to look at the log but I totally called this. You need to get a new tuner because the one you have doesn't know what the fuck hes talking about. Your turbo, per the MFG is good for 56 lbs/min or 560 HP. Another member had a slightly larger turbo (60 lbs/min) and was putting down 550 to the wheels...with a TMIC and 3" turboback.

Let me take a wild guess and say you're making less than 450 WHP. Am I close?

Looking at the logs:
1. If you have a 3.5" intake, you are only flowing roughly 400 WHP of air (give or take). I think you probably have a smaller intake though.
2. If you were out of turbo, you'd be at 100% WGDC. You're not (this means your tuner is lying to you, you barely touch 80% WGDC @6400 RPM)
3. You're only running 15.5 deg timing at/past 6k RPM so I know you're not on a corn mix or some other higher octane fuel
4. 72% MAX IDCs also suggest you're either running aux fuel, or a smaller than 3.5" intake. Someone with a known good tune up can look and post up what power they are making at 240 g/s massflow.
5. Speaking of MAFCALs, your AFRs appears to be all over the place. Either you have a shitty aux fuel tune, or just a shitty MAFCAL, or some issue with the intake system that's gone un-diagnosed (your tuner should have caught this and mentioned it to you)

I hope this tune didn't take more than a couple days/revisions; I also hope you didn't pay much for it.
 
Enki said:
Just about to look at the log but I totally called this. You need to get a new tuner because the one you have doesn't know what the fuck hes talking about. Your turbo, per the MFG is good for 56 lbs/min or 560 HP. Another member had a slightly larger turbo (60 lbs/min) and was putting down 550 to the wheels...with a TMIC and 3" turboback.

Let me take a wild guess and say you're making less than 450 WHP. Am I close?

Looking at the logs:
1. If you have a 3.5" intake, you are only flowing roughly 400 WHP of air (give or take). I think you probably have a smaller intake though.
2. If you were out of turbo, you'd be at 100% WGDC. You're not (this means your tuner is lying to you, you barely touch 80% WGDC @6400 RPM)
3. You're only running 15.5 deg timing at/past 6k RPM so I know you're not on a corn mix or some other higher octane fuel
4. 72% MAX IDCs also suggest you're either running aux fuel, or a smaller than 3.5" intake. Someone with a known good tune up can look and post up what power they are making at 240 g/s massflow.
5. Speaking of MAFCALs, your AFRs appears to be all over the place. Either you have a shitty aux fuel tune, or just a shitty MAFCAL, or some issue with the intake system that's gone un-diagnosed (your tuner should have caught this and mentioned it to you)

I hope this tune didn't take more than a couple days/revisions; I also hope you didn't pay much for it.
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well the turbo isn’t out of steam yet. this is a stock motor so this is where he was comfortable tuning too. I have a 3.5 inch intake and 3 inch exhaust that splits down to 2.5inch at the y. I am on a e30 mix I have a 91 tune as well but that was my e30 log. As far as the afr issue the car has had it since I bought it stock years ago. I could never figure it out but it doesn’t spike too lean ever so I just gave up. Am I really missing out on power just because the tune? This thing rips right now
 
If the turbo isn't out of steam and you're keeping the power down because of the stock block. Why are you even concerned about a 3.5in exhaust for more power? You have more power on tap, you're just not using it.
 
udntknw said:
If the turbo isn't out of steam and you're keeping the power down because of the stock block. Why are you even concerned about a 3.5in exhaust for more power? You have more power on tap, you're just not using it.
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I just figure the power can be made easier and with less boost with a bigger exhaust
 
Haedenjames said:
well the turbo isn’t out of steam yet. this is a stock motor so this is where he was comfortable tuning too.
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Keeping it safe on stock block is respectable; that's fine. However, your current tuner doesn't know how to do that properly. I can't make you change, but when you pop (and you WILL pop), all our collective posts in this thread will be hindsight (the bitter kind).

Haedenjames said:
I have a 3.5 inch intake and 3 inch exhaust that splits down to 2.5inch at the y.
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I've looked at another log from another car and it looks like you probably have aux fuel. That said, you might have an aux fueling problem that cuases your AFRs to go wonky, with or without it being active... I'd look into that. If you don't have aux fuel, well, then you REALLY have a problem because your g/s air intake is wayyy lower than it should be.

Haedenjames said:
I am on a e30 mix I have a 91 tune as well but that was my e30 log.
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If memory serves, I've seen big turbo pump gas timing cars running what your "e30" timing is at. Drama might be doing this to reduce the number of blown up engines that he makes, but what he doesn't realize is he's not even addressing the issue with his tunes by doing this. I honestly don't think he knows enough about these cars to understand what he's doing wrong, even after I told him some of the stuff he was doing wrong years ago. This forum is overflowing with examples of Drama done goofed stuff; just search for dramatuned and pick at random.
I'm telling you man, I've seen several Drama cars blow up this past year and yours is on borrowed time. If you get tuned by a reputable tuner you will wind up amazed at how much better it runs AND you will be able to rest at night knowing it will last longer.

Also if I was your tuner I'd not tune you until you got that AFR shit fixed. That's asking for trouble down the road.

Haedenjames said:
Am I really missing out on power just because the tune?
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Yes. A lot of it, judging by this log (unless it's not a final log). What revision number is it? Also do you know what kind of power it's making?

Haedenjames said:
I just figure the power can be made easier and with less boost with a bigger exhaust
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The most "efficient" way to make serious gains in power from where you are right now are with minor headwork and cams; at that point, you might as well build the motor. Letting the engine flow easier with those two mods will drastically improve performance, even on a 3" exhaust. Like I said, VashExe made 550 wheel at (iirc) the same boost you're running right now, on a TMIC and 3" exhaust but with headwork and cams.

I know what you're thinking: Would a 3.5" exhaust help him make more power?

Actually, no. The turbo was maxed out; can't cheat physics.

The fact that your tuner told you this was needed goes to show he has NO idea how engines *actually* work. Pull the ripcord man. Seriously.
 
Haedenjames said:
my tuner says I should be making 480ish 28 psi on e30. There’s not an awd dyno near me
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My bad, just saw this.
You don't need a dyno, just that log you posted and VirtualDyno. Use custom correction factor of 1.01 smoothing 3, and make sure you populate the car and tire size stuff properly too.

While anyone here can download your log and run it through for you, I think it's important that you see the results for yourself, by your own hand.
 
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