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S Chassis Technical discussion related to the S Chassis such as the S12, S13, S14, and S15.


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Old 03-24-2020, 08:57 AM   #1
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What can I do if I want more power ?

Hi all , Im wanting to squeeze some more power out of my motor my setup is as below and currently has 280rwhp and 355Nm torque

What can I do next to get some more power without going crazy ?

Was thinking head gasket and studs then I could up the boost some more ? Is this correct ?

Thanks

s13 SR20det
stock internals
Gt2871r already on 18psi
1000cc injectors
Fuel system fully upgraded
FMIC
Nistune
2.5? straight through exhaust
E85

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Old 03-24-2020, 09:21 AM   #2
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Stock intake manifold or "greddy" intake manifold? If it's aftermarket, going back to the stock intake manifold will pick up more bottom end and mid range. No need for a different intake manifold below 500hp.

Are you running an external wastegate or internal? If internal still, going to an external gate can increase your low end torque and top end power too.

I'd look into going to a 3" exhaust also.

All these things could pick up power without raising boost pressure, at least initially. Just making the setup more efficient. I wouldn't worry about head gasket and studs below 400hp unless you plan on overheating it lol.
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Old 03-24-2020, 09:26 AM   #3
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What can I do if I want more power ?

Greedy intake manifold and internal gate . I did a 2.5? exhaust as the car is a roadster with no roof so wanted to keep it quieter and nicer to drive . I was told by the tuner that I shouldn?t boost over 18psi without head studs


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Old 03-24-2020, 02:02 PM   #4
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A muffled and resonated 3" exhaust really shouldn't be much louder if at all.
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Old 03-24-2020, 02:11 PM   #5
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A muffled and resonated 3" exhaust really shouldn't be much louder if at all.
I was in the middle of typing the same thing when my browser crashed

I had a 3" resonated exhaust to a dual tip magnaflow muffler on my gutted ka24e-t hatch. Still one of my favorite exhausts to date. Check out BRM exhausts. Run by a nissan guy out of AZ.

Op if you have a trusted tuner, why arent you having this conversation with them?
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Old 03-24-2020, 06:24 PM   #6
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What can I do if I want more power ?

Who ever goes with just one opinion . So if my 2.5 inch exhaust being a restrictive factor on the MGB , I didnt really want to have to go to 3 inch so if I went to an external gate would this be just as good or better ? Thanks

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Old 03-25-2020, 01:30 PM   #7
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Who ever goes with just one opinion . So if my 2.5 inch exhaust being a restrictive factor on the MGB , I didnt really want to have to go to 3 inch so if I went to an external gate would this be just as good or better ? Thanks

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Yes theoretically a external wastegate thats not recirculated back into the exhaust could alleviate any restriction being caused by your current exhaust when at WOT, if it is properly sized.
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Old 03-25-2020, 03:58 PM   #8
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Yes theoretically a external wastegate thats not recirculated back into the exhaust could alleviate any restriction being caused by your current exhaust when at WOT, if it is properly sized.
I second that opinion. (Who ever goes with one opinion right?)


... with the caveat that a divorced external wastegate is going to be WAY more obnoxious than your supposed 3" exhaust would be.
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Old 03-25-2020, 09:12 PM   #9
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https://zilvia.net/f/showthread.php?...45#post6376145

There you go, OP. Ditch the "Greedy" intake mani and go back to stock to shift your powerband down for more useable power. $50 plus shipping and you dont have to worry about exhaust noises.
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Old 03-25-2020, 09:13 PM   #10
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I second that opinion. (Who ever goes with one opinion right?)


... with the caveat that a divorced external wastegate is going to be WAY more obnoxious than your supposed 3" exhaust would be.

Not if I run the wastegate through a long hot dog muffler under the car


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Old 03-25-2020, 09:15 PM   #11
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https://zilvia.net/f/showthread.php?...45#post6376145

There you go, OP. Ditch the "Greedy" intake mani and go back to stock to shift your powerband down for more useable power. $50 plus shipping and you dont have to worry about exhaust noises.

I can only run a high intake manifold due to the engine bay restrictions and steering in the way


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Old 03-25-2020, 09:15 PM   #12
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Not if I run the wastegate through a long hot dog muffler under the car


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I think you're trolling us here. Well played.
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Old 03-25-2020, 09:16 PM   #13
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What size wastegate would you guys recommend ?


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Old 03-25-2020, 09:18 PM   #14
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I think you're trolling us here. Well played.

Haha not at all just want to get the best solution , I see it to be cheaper to go external wastegate than redoing the whole exhaust to 3? plus I do prefer it to be quieter


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Old 03-26-2020, 09:21 AM   #15
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cams? plus boost?
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Old 03-26-2020, 10:18 AM   #16
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cams? plus boost?

I?m already on 18psi and was told that shouldn?t go higher with stock internals . What internals would I need to go higher ? Just head gasket and studs ? Or more ?


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Old 03-27-2020, 09:27 AM   #17
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I think we're on the right track with external wastegate.

As far as cost difference it really depends on what a shop is going to charge you. Sometimes a manifold with external gate could be more expensive than some new exhaust piping.
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Old 03-27-2020, 09:31 AM   #18
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I think we're on the right track with external wastegate.

As far as cost difference it really depends on what a shop is going to charge you. Sometimes a manifold with external gate could be more expensive than some new exhaust piping.

I do all the work myself so it?s just materials cost really . Today I brought a Turbosmart ultra-gate 38mm . I?ll modify my current manifold and add the external gate flange to it, mount the gate and then plumb it to under the car . Should be pretty straight forward. If it?s too loud I?ll add a hot dog muffler onto it feather than plumb it back into the exhaust


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Old 03-28-2020, 06:48 AM   #19
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Reintroducing you’re externally gated flow stream further down in the exhaust will help alleviate back pressure at the discharge of the turbo and keep things quiet.

18psi is relatively tame on that turbo. I would suggest studs and a gasket and more boost without tremendous modifications for more power. You’re already on E85. Cams will shift the powerband to the right, omitting anything the stock intake manifold adds back. I wouldn’t go more aggressive than 264’s if you do choose that route.

Ultimately, you have a lot of choices, but this is just one opinion...
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Old 03-28-2020, 07:08 AM   #20
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What can I do if I want more power ?

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Reintroducing you?re externally gated flow stream further down in the exhaust will help alleviate back pressure at the discharge of the turbo and keep things quiet.

18psi is relatively tame on that turbo. I would suggest studs and a gasket and more boost without tremendous modifications for more power. You?re already on E85. Cams will shift the powerband to the right, omitting anything the stock intake manifold adds back. I wouldn?t go more aggressive than 264?s if you do choose that route.

Ultimately, you have a lot of choices, but this is just one opinion...

Thanks for the advice , how much boost do you think I could run after studs and head gasket ? What gasket and studs would you recommend ? I thought reintroducing the wastegate to the exhaust further down wouldn?t be as effective as keeping it separate


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Old 03-28-2020, 10:18 AM   #21
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Thanks for the advice , how much boost do you think I could run after studs and head gasket ? What gasket and studs would you recommend ? I thought reintroducing the wastegate to the exhaust further down wouldn?t be as effective as keeping it separate


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After studs and gasket, you?d be able to max the turbo. For reliability?s sake, keep it at 22-24. Figure on 10hp per psi of boost.

While keeping them separate is a better solution, packaging constraints may not allow a ?muffler? to be added to the ?screamer? pipe. The point of keeping them separate is because of the turbulence created at the wastegate/turbo outlet. If you look at the EFR series turbos, all wastegate outlets are angled back into the exhaust stream, rather than having to make that flow path turn 90* back into the exhaust path.

I?ve had great experience with Apexi and Cosworth gaskets. I prefer Apexi over Cosworth simply because of the lack of a fire ring on the Cosworth. As for studs, ARP makes a great product and you can get by with their off the shelf variety for the SR. If you intended on going big, I would recommend Mazworx ?bullet end? studs because they bottom in the threaded holes, utilizing all threads available.
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Old 03-28-2020, 10:28 AM   #22
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I?m already on 18psi and was told that shouldn?t go higher with stock internals . What internals would I need to go higher ? Just head gasket and studs ? Or more ?
It doesn't matter how much boost you are using. Boost pressure of 18psi has no relevance to combustion pressure which could be over 1000psi.

Stock internals I would stay under 450rwhp dynojet using E85
All sr20det engines need cam upgrade. It fixes the high rpm volumetric efficiency the engine is capable of, more power with less boost pressure. The reason we like less boost pressure is because its less risk blowing apart the plumbing/clamps, not because it might blow the engine or gaskets. What blows the engine up is hot air, which high boost pressure gets blamed for, and also boost leaks, which causes hot iat AND high EGT, which again high boost pressure gets blamed for. And finally if you exceed the stress that factory parts can handle, something can bend or break. Engine torque is provided by an integral of pressure over some crankshaft radii, so for example you can generate a lot of torque with a sudden push, or the same amount of torque by pushing gently for a longer time while the crankshaft turns. So it could be safe for example to use 500ft*lbs of torque on a factory rod if the push is done over a long time frame of rotation of the crankshaft (using cold temperature and high octane fuel this is what happens) but you couldn't make the same amount of torque using a high temperature and lower octane fuel because the pressure will spike before the crankshaft has a chance to move the piston out of the way (the reaction happens too quickly). So it really comes down to control, tuning, awareness, how much torque the bottom end will handle.

E85 is the ideal choice for cast piston engines. I Would say camshaft upgrade, and focus on the turbine/exhaust (make sure the exhaust is as free flowing as possible). This will maximize the effects of boost pressure on the intake side and minimize the efficiency losses and heating on the exhaust side. That turbo is tiny for that engine so it won't take much. I wouldn't bother messing with nickles and dimes at this point (wastegates/intakes/minor bs trying to gain 20hp). A cam upgrade is worth 20-30% power for example (80hp~), if the turbo can support the flow rate. if you max the turbo and want more power you simply use a larger turbo.
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