Mi16 With Jenveys Mapped At Emerald

[Bakes100 20 1 Cars]

I also discovered this bolt was missing on mine when I removed the gearbox, I wouldnt be comfortable using it in anger without it though.

[hoodygoodwood 70 3 Cars]

I am sure I recently read about someone who experimented with trumpets on throttle bodies and found the best combination was 2 short and 2 medium length ( or 2 medium and 2 long ) , it gave a combination of each characteristic . Was possibly on here or maybe on youtube .

[allanallen 528 2 Cars]

There was a guy over on the 6 forum who used different length trumpets, I was sceptical of his results though as he claimed to have made (from memory) around 220bhp from an otherwise standard gti6 engine.

 

Great results on the mi though

[Sandy 189]

Very suspect on that one, a fairly small change in trumpet length/shape can cause up to around 25% change in fuelling needs at certain speeds/loads and unless you have 3D cylinder trim over all loads/speeds, you can't map the engine accurately and safely. Also what you are trying to do essentially, is spoil/improve cylinder pairs at different loads/speeds, which will always be a compromise. Some of the high end bike engines use different length trumpets, but the priorities of bike engines are quite different and the dynamics of their operating ranges, very different! The stackable trumpet length method, eg on the Xsara F2 engine, is a lot more credible, but the speed of operation required and engineering it are big problems to solve, for moderate benefits. There's a lot more to be had from testing different static pipe tuning options with engine dyno time.

[allanallen 528 2 Cars]

Just to add, the above mentioned gti6 was running a standard socketed marrelli ecu so I'm guessing it's capable of trimming the fueling for individual cylinders?

[welshpug 1,622]

they are sequential but you'd need a different map essentially for the differing pairs, i'm not sure the MM1ap ecu can do that.

[Sandy 189]

Yes, the fuelling would need to very for each pair on 3D load+speed. Even if you did achieve that, the benefits of each length at each point where it does make a difference, would be halved effectively. Bike engines use this and other tricks to smooth and widen the torque curve, for best traction and predictability, but compromise the higher torque points to do so and operate over a much wider RPM range. Between 4-8KRPM as we're typically talking here and with adequate traction for the power in most cases, our objectives are different. I like to get a slug of torque from 4-6KRPM where possible, it makes a big difference to the overall performance on H-pattern cars.