Board logo

Thinking out loud........
Jon Ison - 26/6/08 at 08:07 PM

Bike inlets ?

How detrimental to power/running would it be if you extended the inlet tracks between head and throttle bodies with a slight bend to keep heights down under bonnet ?

Anyone tried anything like this ?


smart51 - 26/6/08 at 08:39 PM

It would mean that the tuned frequency of the inlet track / cylinder is lower. This has 3 effects. 1 is that peak torque is lower in the rev range, 2 is that bottom end torque is improved a bit. 3 is that top end power will be reduced a bit.


Jon Ison - 26/6/08 at 08:45 PM

quote:
Originally posted by smart51
It would mean that the tuned frequency of the inlet track / cylinder is lower. This has 3 effects. 1 is that peak torque is lower in the rev range, 2 is that bottom end torque is improved a bit. 3 is that top end power will be reduced a bit.


2 out of 3 favorable results or certainly ones you can live with ?


mark chandler - 26/6/08 at 09:21 PM

Injected my 893 blade engine and made a bent manifold to hold the 954 throttle bodies, engine feels much stronger low middle range. More power definately as I had to uprate the clutch afterwards as it started to slip at 8k ! Rescued attachment Inlet_plenum_Front_small.jpg
Rescued attachment Inlet_plenum_Front_small.jpg


ChrisGamlin - 26/6/08 at 09:33 PM

Ive seen it done on a busa as well, with much longer inlets. In Mark's case he's upgraded to throttle bodies so that in itself would account for the increased performance, but I suspect like for like with the same carbs / TBs then it might boost the mid range a smidge but Id be suprised if you didnt lose out overall, otherwise the bike manufacturers would do it.


mark chandler - 26/6/08 at 09:55 PM

Bikes are about packaging, get it all under the tank and quiet.

I am using the same air filter and exhaust, carbs were dyno jetted which pulled the power up a bit at the time

Apart from power the sensitivity of the throttle makes the car much harder to drive now at slow speeds, this is definately down to the TB's as the carbs are damped.

Regards Mark


Jon Ison - 27/6/08 at 07:21 AM

Not looking for it to improve performance just wondering how much if any it would cost. What I was/am looking for is not having to cut the bonnet.

Agree with Mark to, whilst performance is on bike manufactures minds getting everything in the frame under the tank is also a big consideration.


mark chandler - 1/7/08 at 11:47 PM

Mine cost:

Megasquirt £125 basic kit
TB's Ebay £85

Bit of tube free

JAW ~£50 to set it all up.

MS needed fiddling with to recognise the bike tach output, bridged a resistor and some of the pins, its described in the forums.

Regards Mark


foes - 2/7/08 at 09:34 PM

quote:
Originally posted by Jon Ison
Bike inlets ?

How detrimental to power/running would it be if you extended the inlet tracks between head and throttle bodies with a slight bend to keep heights down under bonnet ?

Anyone tried anything like this ?


hmmm, i was thinking exactly the same thing this evening as theres a front engined r1 converted mini in this months pratical performance car and he's done this to clear the bonnet...

So how much top end power would it likely lose...?