Bike Bodies - What Is The Real Difference Compared To Aftermarket Bodi

[Dream Weaver 2]

I've had my bike bodies on the car now for 800 miles.

 

They seem to work in that they provide air into the engine, they look & sound excellent, cost half the price of a proper Jenvey/KMS, and apart from the throttle linkage issue which i'm sure could be sorted out by someone in a machine shop, they have the theory to work perfectly.

 

But..apart from Damien's GTI-6 which made 192bhp, no-one else has managed any significant numbers. My engine made 180bhp on std induction, but has dropped to 173bhp on the bodies, 16v205 (Rich) made only 140bhp on his bike bodies which jumped to 176bhp on Jenvey IIRC.

 

And this annoys me!!

 

Throttle bodies are just a tube with a butterfly valve in the middle. You press the loud pedal and they open allowing air through which mixes with fuel.

 

Apart from injector position, I can't see any significant difference between a bike body setup and a Jenvey or KMS setup - bike bodies have the injectors in the original Mi16 location, Jenvey etc have them further away in the actual bodies. Trumpet length could be an issue, but my setup is as close to the Jenvey/KMS setup as it can be.

 

Surely this positioning/trumpets wouldn't cause a 20-40bhp power loss? Torque loss may be due to inlet tract length but I dont know.

 

So what else could be causing the issues? Are there other areas that could affect the power, exhaust, head, injectors etc, although in the case of Rich's setup it was only the bike bodies that were different?

 

I've started buying up the bits for a proper KMS body setup now, but it will cost £600 over the bike bodies (which I will need to sell), and there is no gaurantee that it will be any better than the current setup.

 

If I spent the £1,100 in total to find it wasn't much better i'd be gutted.

 

Just to add to this, i'm doing a RR day at prosport with the Subaru boys on Saturday so will get a good power run now that my linkage is sorted compared to how it was at Mikeanics.

Edited October 11, 2006 by Dream Weaver

[Guest ashnicholls]

Flip, cant see why they would lose power either, thats useless.

 

As you say its a common trend?????????????

[smckeown 1]

arent you using those cone filters ? haven't I ready that they can sap power ? Didn't you also menion that the butterly was opening too far and actually restricting peak flow ?

 

Other than those 2, I can't see why your car isn't showing more power, unless it's the previous rollers showing crap results

[Adnic69 0]

I am baffled by this too as there appears to be no real reason why they don't give as much power.

What would be good to know is what Damien has done differently if anything to others.

Now that the pug is back on the road I will be adapting my mangoleti manifold to fix my bike tb to. I was going to base my design as close as I can to a normal 8v setup. Hoping that I should see around 160 bhp.

[smckeown 1]

ah that's a point, could it be your inlet has not been ported to match the TBs and head ?

[Sandy 189]

It's my opinion obviously and will probably be lambasted, but the following factors seem to be common to bike bodies conversions:

 

*Unequal manifold design, the tracts aren't smoothly shaped or are wildly different in shape to get from the port spacing to the bodies spacing, maybe featuring sharp angles of distortion from bending, even different lengths between cylinders.

 

*Silicone hose connections, which rarely offer a smooth tract and a friend of mine who tried to use silicone hose to vary inlet length on his dyno, found that the results didn't correlate with a solid tube of the same length; why this is isn't exactly clear, but I can't dispute his findings.

 

*Short tract length overall, which is a pretty sure fire way of losing mid range and even peak power in some instances, the main reason I believe why some TB systems appear not to perform as well as the plenum inlet they've replaced.

 

*Injector position, again, two friends of mine have worked extensively on varying injector position, on Colin's engine he saw 10bhp gained and lost by using outer and inner injectors at peak power. Mounting them half way up the tract will obviously be a halfway house, literally.

 

*Bore diameter, which i've never found to be as critical as overall length of the tract, but a 40mm TB has about the same flow potential as a 36mm pipe. There's alot of advice about that suggests smaller is better with bodies, but I personally don't subscribe to that, if you have 40mm ports on the head (like the Mi16), you should have 45mm bodies at least. Bigger than that won't gain you anything, but any smaller and the TB's become the restriction. The argument against is that the throttle progression deteriorates as the TB size is increased, but that's mostly down to mapping. I've runa TU 1.4 8v on 45mm TB's and once the map was nicely honed, it was very progressive.

 

*Bell mouth, if you don't have a nicely radiused end to the tract, the air around the perimeter will be turbulent and stall air coming into the tract, effectively providing a restriction. Sock filters may also spoil this area.

 

*Air supply, not such a problem on the move as engine bay air temp (unless directly behind the rad) usually drops to somewhere near ambient, but on the rolling road it can be very high, leading to potentially poor mapping and poor power results.

 

I could go on, but now my fingers are tired!

[Dream Weaver 2]

The inlet is ported to match the TB's perfectly. If you look inside with a torch you can see all the way down to the valves in a nice smooth transition.

 

I got rid of the cone filters and it seemd to help with the pickup, so it now runs proper 65mm long trumpets (from the TB's) and new ITG filter as per the pics below. I've also sorted the linkage now using the original throttle cam and stop, so it now opens from vertical to horizontal with full pedal travel, but I have to put up with it being a pig on light load again

 

Could too much oil on the filter cause issues???

 

It would be easy for me to sell them now and fit a proper KMS kit, but I just have a niggle as I never ever like to give up on anything I do, so it would bug me to just give in now.

 

If I put the KMS kit on i would expect to get around 185bhp, so I want to know how the proper kit gets that extra 12bhp??

 

Some pics of the setup as it is now just as a reminder:

 

 

[Dream Weaver 2]

It's my opinion obviously and will probably be lambasted, but the following factors seem to be common to bike bodies conversions:

 

*Unequal manifold design, the tracts aren't smoothly shaped or are wildly different in shape to get from the port spacing to the bodies spacing, maybe featuring sharp angles of distortion from bending, even different lengths between cylinders.

 

*Silicone hose connections, which rarely offer a smooth tract and a friend of mine who tried to use silicone hose to vary inlet length on his dyno, found that the results didn't correlate with a solid tube of the same length; why this is isn't exactly clear, but I can't dispute his findings.

 

*Short tract length overall, which is a pretty sure fire way of losing mid range and even peak power in some instances, the main reason I believe why some TB systems appear not to perform as well as the plenum inlet they've replaced.

 

*Injector position, again, two friends of mine have worked extensively on varying injector position, on Colin's engine he saw 10bhp gained and lost by using outer and inner injectors at peak power. Mounting them half way up the tract will obviously be a halfway house, literally.

 

*Bore diameter, which i've never found to be as critical as overall length of the tract, but a 40mm TB has about the same flow potential as a 36mm pipe. There's alot of advice about that suggests smaller is better with bodies, but I personally don't subscribe to that, if you have 40mm ports on the head (like the Mi16), you should have 45mm bodies at least. Bigger than that won't gain you anything, but any smaller and the TB's become the restriction. The argument against is that the throttle progression deteriorates as the TB size is increased, but that's mostly down to mapping. I've runa TU 1.4 8v on 45mm TB's and once the map was nicely honed, it was very progressive.

 

*Bell mouth, if you don't have a nicely radiused end to the tract, the air around the perimeter will be turbulent and stall air coming into the tract, effectively providing a restriction. Sock filters may also spoil this area.

 

*Air supply, not such a problem on the move as engine bay air temp (unless directly behind the rad) usually drops to somewhere near ambient, but on the rolling road it can be very high, leading to potentially poor mapping and poor power results.

 

I could go on, but now my fingers are tired!

 

Cheers Sandy, all good valid points, but none applies to my setup really.

 

1. My runners are all equal length and ported to the bodies.

 

2. The silicon joiners are present, but they are flat and smooth with the inlet manifold/TB's so there are no spaces between inlet face and TB's.

 

3. The tract length is pretty much as per KMS/Jenvey

 

4. I had read that injectors closer to the valves would produce better low down torque/mid range.

 

5. They are 42mm bore, enough for over 200bhp according to Jenvey.

 

6. Std Weber radiused bellmouths

 

7. Lowered radiator, so air flows straight through the grill and modified cowling into the filter, ambient inlet temps when running.

 

Hence why I'm stumped

[Sandy 189]

That only really leaves engine health, exhaust, cam timing or mapping then.

[damien 22 1 Cars]

maybe i was just god dam lucky to get mine up and running

 

any chance of of close up pics of you manifold and throttle cam?

[Dream Weaver 2]

I've plenty of pics, but not sure which ones I could put up to help with the diagnosis.

 

How is yours setup Damien?

 

1. Have you used trumpets as your filter seems half the size of mine?

 

2. How do your bodies connect to the manifold?

 

My RR day on Saturday may give more clues.

[Dream Weaver 2]

One other thing, what about injectors?

 

Mine is still on the original Mi injectors, so maybe swapping them out may help?

 

I have some Saab reds here but they are unknown, and when I tried them the first time it wouldn't run properly.

[smckeown 1]

the emerald software should tell you if you are close to max duration. I did read 180bhp is around the maximum for them. Also if they are, surely mikeanics would save said something.

[Dream Weaver 2]

Mikeanics didn't really do or say much in all honesty

 

I'll have to do the 600 mile round trip to Dave Walkers next time!!

[smckeown 1]

here's a screen show from my KMS map

 

 

"The thin yellow line in the graphs of the injection diagram indicates the maximum duration of injection for the engine speed concerned."

 

Emerald is bound to have something the same...

[pug_ham 240 3 Cars]

*Short tract length overall, which is a pretty sure fire way of losing mid range and even peak power in some instances, the main reason I believe why some TB systems appear not to perform as well as the plenum inlet they've replaced.

Sorry for the o/t but isn't this what explains why some 106 GTi & Saxo VTS owners experience a drop in power & torque when they take the next logical step & fit TB's instead of the standard system?

 

Injector placement could be an issue but I'm sure that on Jenvey or KMS TB's they are no longer in the same place as the standard inlet manifold so that throws that idea out of the window imo.

 

Graham.

[Sandy 189]

Sorry for the o/t but isn't this what explains why some 106 GTi & Saxo VTS owners experience a drop in power & torque when they take the next logical step & fit TB's instead of the standard system?

Yep, they almost always use the Chadil manifold, which is designed to keep DCOE carbs at an angle which won't upset them and that means pointing straight at the brake bar, limiting inlet tract length to about 290mm, some way short of the 340mm I ran with the Jenvey bespoke manifold and single bodies (106 GTi engine in a 205, but later transplanted into a 106 Rallye). Mine made so much more mid range than was typical, that my graphs were generally discredited at the time and that was with a standard head and cams.

 

Injector placement could be an issue but I'm sure that on Jenvey or KMS TB's they are no longer in the same place as the standard inlet manifold so that throws that idea out of the window imo.

It doesn't really, because being further upstream (by about 100mm when in the bodies vs std location) significantly increases the mixing time before the charge enters the cylinder, it also places the nozzle in the turbulence off the back of the butterfly, which helps full throttle and high rpm quite alot, but not part throttle and idle/emissions.

[Adnic69 0]

Just a thought. Why did you not stick with the bike injectors?

I have the same tb's as you I think(gsxr 1000) and was told that the standard injectors on them were good for 200 bhp easy.

[damien 22 1 Cars]

I've plenty of pics, but not sure which ones I could put up to help with the diagnosis.

 

How is yours setup Damien?

 

1. Have you used trumpets as your filter seems half the size of mine?

 

2. How do your bodies connect to the manifold?

 

My RR day on Saturday may give more clues.

 

this is a pic of the kit before fitted to the car, as you see theres rubber black trumpets. ive cut them so they are all the same size inside the filter.

 

 

i had problems with that manifold as it didnt clear the PAS so i got the standard gti6 manifold cut so it would clear the PAS, then from the gti6 manifold it was weld onto the manifold you see above then the silicone hose (as on the above pic.

 

im running the OE gti6 injectors

[Dream Weaver 2]

So I guess its not the trumpet length at fault then as I would've thought my 65mm trumpets would be better than the rubber ones you have there?

 

Adnic - I didn't get the injectors with the bodies, but i'd read in a few places that the injectors up near the head would be better for low down figures anyway.

 

Sean, I do have the injector details and remember viewing them in the last data logging session I did - I'll have to have a look at the graphs again.

 

I wish I had my own RR, we could test a few different things then

[welshpug 1,622]

Seeing as the first map was produced with a throttle pedal/butterfly not performing as it should and the TPS notreading the correct information the first step should be a mapping session.

[Dream Weaver 2]

I think it was mapped fine, the pedal issues started after he'd finished, but you may be right. I'll see what happens Saturday as they are doing diagnostics as well as power runs.

[welshpug 1,622]

right, good thinking batman!

 

if they do a diagnostic run with a gas analyser youll see if its fuelling correctly on WOT through the rev range, but it wont point to any innaccuracies on part load.

[veloce200 3]

6. Std Weber radiused bellmouths

 

carb bellmouths should not be used on fuel injection set ups - this could be the reason !!! stick some proper injection trumpets on - worth a try

 

also the injectors may well be maxed out - what is their flow rate ?

Edited October 11, 2006 by veloce200

[Sandy 189]

If they are max'd out I would have expected the mapper to convey that to him? Stranger things have happened though.