Tem120

iTrader: (5)

alright so I've done some reading . and I know the benefits of exhaust porting usually go to waste with the twins because the oem manifold

BUT , I look at hte OEM manifold and its bigger then the stock ports , So theoretically if my exhaust got ported just enough to match the OEM manifold ports .

I SHOULD get quicker spool from the twins correct? Or am I missing some sort of math.

geopouros

iTrader: (1)

u will but come on now u will open ur engine up to port and keep the stock turbos? stock turbos spool up from 2000rpm do u need them to spool even faster?
porting helps in a lot issues vending more exhaust helps reducing head and yes more power on bigger turbos stock ones run out off air on 320bhp... so if u port ur engine u will need to upgrade
turbos as well to see all the plus off porting?

Tem120

iTrader: (5)

Upgradding turbos is something that will happen just not right away , and the reason for wanting increased spool is in order to make the secondary turbo open up sooner .

if I can get it to spool quickly even if I open them up at 3500 rpms VS 4k rpms

94RX7R2

My second turbo spools just after 4500RPM

Tem120

iTrader: (5)

I have a power FC which lets me dictate when my secondary turbo opens , but no point in making them open up at 2k rpms if they wont be spooling much

djseven

iTrader: (56)

You will not get quicker spool from exhaust porting. I'm still baffled at what exactly you are trying to accomplish? If you have stock twins and stock ports. Spool up isn't getting better unless you go to 9.7 rotors and 99 spec twins.

Tem120

iTrader: (5)

ok , Just wondering what benefits I'd gain from exhaust porting then . I thought that was the point to it. if the exhaust ports are bigger more exhaust should flow through them and thus spinning The turbos quicker no ?

kind of like how opening up your exhaust quickens spool.

Ofcourse I also understand that there is less resistance to force the exhaust through a larger hole big straw vs small straw . when under load. reducing backpressure in the housing .

djseven

iTrader: (56)

I'm on my phone and don't have time to explain. The stock exhaust ports far out flow the factory intake ports. Consider how long the exhaust ports are open vs. intake ports. If you are not familiar with the inside of the engine, how the rotors/seals pass over the ports it won't make sense. Trust me, the last thing you need to do is port the exhaust ports.

Tem120

iTrader: (5)

Intakes are already getting ported . that is being accounted for . but i figured I'd port the exhaust in order to match the intakes . I didnt know that hte exhaust ports outflowed the intake ports that much .

Narfle

iTrader: (16)

You clearly want to port your exhaust and are just fishing for someone to tell you it's a good idea, so just do it already.

The stock turbos already spool almost instantly, you probably won't notice any difference. Even if there were a difference it would be small and well below the usable power band.

We're looking at marginal gains at best for a lot of work/time/money. I think we're all driving at the fact that you'd be much better off focusing on some major aspect of your build.

djseven

iTrader: (56)

Stock exhaust ports are plenty for well over 600hp.

Tem120

iTrader: (5)

Major aspects have been taken care of I'm trying to learn. its not about clearly wanting to port my exhaust. I just dont want to have regrets after the engine is together then i tell myself damn I wasted 5 grand on the motor build and I was to cheap to waste a bit more on ported exhaust and I would of gained X X from it .

Tem120

iTrader: (5)

Thank you I dont plan to make NEARLY that much ever..

Again just an exercise in curiosity

what are the downsides of porting the exhaust ? more overlap , so loss of low end torque?

anything else ?

Speed of light

iTrader: (8)

I have ancedotal evidence that exhaust porting does help spool, at least in the case of my BNR twins. However, and this is a big however, you remove the reversion step at the port/manifold interface which may be detrimental at higher RPM & loads; especially with twins--since the turbos are the principal restriction.

Tem120

iTrader: (5)

Thanks everyone for all the advice

arghx

iTrader: (3)

I've spoken my peace in another thread. Another vote for no porting of exhaust if the goal is improved spool. The change in timing would not be advantageous.

fendamonky

iTrader: (6)

Porting, in general, will push your usable power curve higher in the rpm range. You'll gain some extra ponies, but you'll also lose power in the low to mid range.

It all boils down to what you want, and what you're willing to lose in order to get it. I have a mild (I believe) street port in my car, personally I would never consider going more than that... there is a guy on RCC making regular, reliable, 600whp+ using stock ports with CRAZY streetability and power all through the revs.

BLACK MAMBA

iTrader: (58)

My stock exhaust port and RE matched intake ports are pushing 592hp without issues.

94RX7R2

I do too but I just have exhaust and intake with stock boost. I made 277hp with the "base tune". Does anybody know if my power will increase with a lower RPM spool? My next upgrade is probably a new intercooler and then I could raise my boost safely.

Tem120

iTrader: (5)

not unless you werent making target boost for some reason ,

But quicker spool will give you more power sooner, wider powerband .


I only made 298 at 14psi but this was a month before engine blew hah