28 mm headers vs. 32 mm headers on drwa through GSX1100

[Stephtell]

Right then,

 

I've recently purchased an 1100 which has been fitted with a draw through turbo system.

 

Now the headers are currently 28 mm BUT I'm considering upping them to 32 mm just because the material to do so is available.

 

However, I'm wondering what effect you lot would expect to see from the change...

 

On the one hand I'm assuming gasspeed will decrease due to the larger diameter, thus slowing down spool up on the turbo, however the gasvolume should increase so that part might level out.

I'm figuring it will make it easier for the engine to breathe so temps should be lower and maybe it should make some more power...

 

What do you think?

 

Cheers,

 

Steph

[Stephtell]

No-one?

[slingy1157]

Mate, I think you pretty much hit the nail on the head in your first post. Boost will start a bit later and there may be the potential for more top end power but that would still depend largely on the spec of the turbo itself as to what is the biggest restriction in the the system. Header size, or turbo a/r. But from what I know, I don't think the gains will be noticeable. 

[Stephtell]

Turbo is a ceramic bearing Turbonetics T4/3 hybrid...it's currently running 24 psi of boost and pushes 300 BHP.

 

It would be interesting to test both headers on the same day, on the same bench...I do have previous experience on a turbocharged car where fitting a larger bore exhaust system made it possible/nessecary to deliver a significant ammount of extra fuel to the engine and it made a good ammount of extra power.

[Arttu]

I have been told that 28mm ID shouldn't cause any significant restriction below 400hp. I have that size on my GSX1100 and it outputs about 300hp. Compared to boost level, rpm and other engine details this seems to be quite good result and I don't it would gain much power with larger header size. However, this is a blow through system and I'm not sure if a draw through with longer header would be different. But for example Orient Express funnybikes (about 600hp) were using quite small headers back in the days, not larger than 28mm ID I would guess.

It would be interesting to compare different headers designs in dyno, indeed. Unfortunately it's rare to see this kind comparable test results anywhere.

 

[Stephtell]

Well, I might fabricate a 32 mm header and run them both on the same day and the same dyno...won't be for a while though

[FJD]

pretty interesting theme - do you leave the collector pipe to the turbo like it is ?

[Stephtell]

Yes, that is the idea...I'm thinking it should produce more power and leave the engine running a little cooler...