Gti6 4-2-1 Exhaust Manifold

[Toddy 7]

Does anyone have experience of an off the shelf/Custom 4-2-1 manifold for the GTI6 engine?

 

My thinking is while the std 4-1 GTI6 manifold produces better torque than an Mi, there is still room for improvement as seen on some modified engines i.e. Dixons 1.8 - Built by Sandy.

 

Also other manufacturers engines i.e. the Honda K20 can be increased from 145Ib/ft to 167 Ib/ft etc

 

Considering this for mildly tuned GTI6 engines.

 

Cheers

[Anthony 1,003]

I know that Miles is planning to offer something along these lines soon (if not already)

 

22lbft gain from just an exhaust manifold though? That sounds laughably optimistic to me, especially on what is already a 100hp/litre engine

[Toddy 7]

I know that Miles is planning to offer something along these lines soon (if not already)

 

22lbft gain from just an exhaust manifold though? That sounds laughably optimistic to me, especially on what is already a 100hp/litre engine

 

 

That's on an elise platform, with aftermarket ECU with Peak ~230 bhp. Obviously cars are built to a price by manufacturers, far cheaper for a compromised 4-1 rather than an optimised 4-2-1, they also have to put the Cat somewhere. Sandy has experience of the K20 may be he can shed some more light on this subject.

 

When I had an MI16 in a 205 I changed from a s*itty Bosal exhaust (without the splitter) to a Janspeed (2.5in downpipe) and the difference in midrange torque was night and day.

[Miles 331 1 Cars]

I have the 306 one made and ready for shipping, The 205 one I'm just waiting on a shell project to arrive so I can make the required adjustments for it to fit, Compared to the Maniflow prices on these I will be allot more competive

[Toddy 7]

I have the 306 one made and ready for shipping, The 205 one I'm just waiting on a shell project to arrive so I can make the required adjustments for it to fit, Compared to the Maniflow prices on these I will be allot more competive

 

 

Have you got some back to back tests proving the benefit of the design?

[allye 530 3 Cars]

Can't wait for you to get these going miles! I imagine there will be a lot of interest, I'll certainly be after one.

[Miles 331 1 Cars]

Afraid not and I can never see it happening unless I add around £35.00 per manifold on for the results and then every engine is different as is every RR, To give you an idea you would be looking not far off £1000.00 for back to back test's with all the time involved and the RR which is out of my hands time wise

[Cameron 16]

Also other manufacturers engines i.e. the Honda K20 can be increased from 145Ib/ft to 167 Ib/ft etc

 

At the risk of starting the torque vs power argument again, those figures are completely meaningless without a figure for rpm.

 

My hunch is that torque was improved in midrange, but reduced at top end - i.e. lower peak power.

 

And please, lbft! Torque is measured by force multiplied by distance.

Edited October 23, 2011 by Cameron

[Toddy 7]

At the risk of starting the torque vs power argument again, those figures are completely meaningless without a figure for rpm.

 

My hunch is that torque was improved in midrange, but reduced at top end - i.e. lower peak power.

 

And please, lbft! Torque is measured by force multiplied by distance.

 

 

Cameron - Many examples below on Dynoplot, manifolds are made by 2Bular and Chris Tullet Exhausts etc, thought you might be one to has provided some useful insight, obviously not!

 

http://www.dyno-plot.co.uk/dyno/dynoplot/id%26sort%3Drec%26but_sea%3Dqs%26sea_simple%3Dhonda%26frcd%3D1/index.htm

 

My early post stated circa 230 Bhp, why do you think that manufacturers outputs can't be improved upon? I expect that type of thought process on the 306 forum, not here.

[Cameron 16]

When did I say manufacturer's outputs can't be improved on?

 

My point is you can't quote the torque figures alone without any reference to rpm as it's completely meaningless. You can quote a 20lbft increase in torque, great! But where did that increase happen? There's a huge difference in performance between a 20lbft increase at 1200rpm and at 6000rpm!

 

Anyone who understands the concept of torque and power knows this and would quote at least torque and rpm, the fact that you can't even get the units of measurement right makes me think you don't understand it at all.

[Cameron 16]

Rant rant bitch bitch..

 

Sorry, think I got out of bed the wrong side this morning.

[Sandy 191]

You can see substantial mid range gains from the right exhaust manifold design, but I would expect a 10% improvement in lbft/litre to only really happen with other changes. Seeing a standard K20 make that change is absolutely possible, but only with improved induction and cam timing revision I would expect.