Exhaust dimension..

[Kokkolanpoika]

Best way to design exhaust manifold primary tube size and lenght for tuned engine?
I spoke to my local race engine builder, he mention that engine power has no big deal for sizing primary tube OD?? He will look more of the engine cylinder capacity and engine rev capapility.. He has got very good excamples how to build powerfull engines.. 3.0 M3 engine made over 380hp N/A..

I have got RV8 5.2litre stage 4.. I´t has got +390hp and 41.5mm primary pipe.. Our race engine builder say it might be give slightly more power ~10hp more at top end if i go for 44.5mm primary pipe..
Dess Hammill´s book also recon 44.5mm primary pipe and also old David Hardgastle book recon 44.5mm primary pipe.

Same think as i wonder why RV8 like big throttle bodies like 48mm to get near 400hp.. John Eales run as big as 50mm throttle bodies on his race engines? And it will make 420hp..

V8 developmets also recon 44.5mm primary pipe to me, and it will slightly hurt low down torque.. Not so important because i have got over 500Nm hole rpm range 2000-5500rpm.

[rev-erend]

So everyone has told you inch and 5/8 is oo small and inch and 3/4 is best .. so will you be changing to the large size ?

[Pumaracing]

I'm not sure how cylinder capacity plus rpm capability doesn't boil back to bhp per cylinder anyway or at least something pretty damn close.

Anyway your current pipe size is good to about 440 bhp by my own charts.

[84Dave]

You could doublecheck the Puma recommendation by purchasing/using PipeMax software from www.maxracesoftware.com . Best software on the planet for dimensioning exhaust systems. -84Dave-

[jimbob82]

+1 for pipe max. I use it and it is full of goodness. If the op wants I can run his info through and paste the output here

[Kokkolanpoika]

I don´t want to spend 45$ some program. I have seen Honda S2000 engine dyno results when they use STD exhaust manifold vs tuned custom made using some stupid program.. STD manifold made 7hp more than new expensive custom item..

But if you jimbob82 want, i can send some details of my engine, so we can look what it say..

Edited by Kokkolanpoika on Monday 11th February 14:23

[jimbob82]

Send me all the info you have and I'll run it through tonight.

The program they used may have been a poop one. Or they made a mistake when inputting the data.

Programs are only as good as the info u put into it. GIGO.

Give me accurate data and as much as you can along with where max power and torque are in the rpm range and we'll see what it kicks out

Edited by jimbob82 on Monday 11th February 14:40