51.5 IDA 48 vent limitations

[hotstreetvw]

Do anyone know off hand how much power 51.5 IDAs with 48 vents can produce?  Anyone have dyno experience with them in the 275hp+ regime?  Roman had a 2789cc with 58s maybe, 48vents, if I recall it made 286hp (little bigger carb, but same vent).

I dyno'd my 101.6x84 yesterday.  It made 203 whp uncorrected (high altitude), 242 whp corrected, which is about 285 flywheel hp corrected.  Peak HP came at 6900 rpm, where my calculations based on valve size and port said it would happen at 7900 rpm.  The power curve peaks then drops some and slowly declines towards 8000 rpm.  It's above 200 whp from 5500 rpm to 8250 where I stopped the pull.   Most graphs I've seen peak and then turn sharply downward.

The engine exhibits a lot of reversion.  There is a fog that develops above the velocity stacks under load, all the way to the end of the pull.  Could this be attributed to being under carb'd? 

https://m.youtube.com/watch?feature=youtu.be&v=Z9V54Im1IwI

[Roman]

Andreas Jönsson had 280+ with 51 mm IDA before switching to EFI. I don't remember what the exact power was.

[Elnef]

Mine 2979 made ca 270 and 17 more with 61
rick dicksons made around 300  if I renember correct

[hotstreetvw]

Do you guys know anything about Rick's car?  I've seen this article, did this engine make 300?

https://www.cbperformance.com/Articles.asp?ID=265

Any thoughts on the reversion?  Or is it pretty typical?

[PPRMicke]

Andreas Jönsson had 280+ with 51 mm IDA before switching to EFI. I don't remember what the exact power was.

282 with 44mm vents ( JPM )
 http://jpmotorsports.se/ms/ms/j-p-motorsport-produkter-helsingborg-254-68/ms-90000825-p-4/#Raptor Venturies
/// Micke

[hotstreetvw]

I like that he has removed the aux venturi/booster.  I would consider them if they would fit 51.5s and came larger than 44s.  44s would put me in the same ball park I am now with maybe better control over AF.

[Udo]

[ Attachment: You are not allowed to view attachments ] 2,4 with 280 HP so far , but the US guy's had more . Must be over 300 because they did 9's with 51's many years ago

Udo

[Udo]

Mine 2979 made ca 270 and 17 more with 61
rick dicksons made around 300  if I renember correct

Does the silver car come back on the track ?

Udo

[hotstreetvw]

I think 300 hp would be obtainable.  My thinking is there are two roads to HP.  Efficiency and flow.  If the IDAs limit flow, one way to raise the peak power would be to increase BMEP (higher compression, more efficient combustion process).  So presumably a pro-stock engine with 16:1, could generate more HP than my engine at 13:1, with the same limitations on the induction side.  They could also be running without venturis, or modified aux vents and boosters.  I've seen pictures of the aux vent being trimmed down so that its not full circle.

So far we have
Romans 2789cc w/ 286hp, 48 vents in 58s (not IDA, but comparable vent)
Elnef's 2979cc w/ 270hp,  made more HP with 61s
AJ's OXY unknown cc w/ 282hp, 44 JPM vents (no booster)
Udo's 2.4L w/ 280hp

[Elnef]

Mine 2979 made ca 270 and 17 more with 61
rick dicksons made around 300  if I renember correct

Does the silver car come back on the track ?

Udo

The silver car rasmus did drive is in finland now
Dicksons light blue/silver I belive its stil in denmark but every go fast parts are sold out

[mikko k]

Mine 2979 made ca 270 and 17 more with 61
rick dicksons made around 300  if I renember correct

Does the silver car come back on the track ?

Udo

The silver car rasmus did drive is in finland now
Dicksons light blue/silver I belive its stil in denmark but every go fast parts are sold out

If you mean this one, I do have it now.
[ Attachment: You are not allowed to view attachments ]

[PPRMicke]

I think 300 hp would be obtainable.  My thinking is there are two roads to HP.  Efficiency and flow.  If the IDAs limit flow, one way to raise the peak power would be to increase BMEP (higher compression, more efficient combustion process).  So presumably a pro-stock engine with 16:1, could generate more HP than my engine at 13:1, with the same limitations on the induction side.  They could also be running without venturis, or modified aux vents and boosters.  I've seen pictures of the aux vent being trimmed down so that its not full circle.

So far we have
Romans 2789cc w/ 286hp, 48 vents in 58s (not IDA, but comparable vent)
Elnef's 2979cc w/ 270hp,  made more HP with 61s
AJ's OXY unknown cc w/ 282hp, 44 JPM vents (no booster)
Udo's 2.4L w/ 280hp

AJ oxy 2594 cc   ( with efi 310++ )
/// Micke

[hotstreetvw]

Micke, do you know what he is running for throttle bodies?

Thanks,
Will

[Elnef]

Mine 2979 made ca 270 and 17 more with 61
rick dicksons made around 300  if I renember correct

Does the silver car come back on the track ?

Udo

The silver car rasmus did drive is in finland now
Dicksons light blue/silver I belive its stil in denmark but every go fast parts are sold out

If you mean this one, I do have it now.
[ Attachment: You are not allowed to view attachments ]

No your car is Roar Lundes old one from norway I think Udo ask about this silver car from us I think also is in Finland now

[PPRMicke]

Micke, do you know what he is running for throttle bodies?

Thanks,
Will

Yes
DUCATI 749/996     ( EFI fultech Ft 500 )
/// Micke

[Roman]

Micke, do you know what he is running for throttle bodies?

Thanks,
Will

Yes
DUCATI 749/996     ( EFI fultech Ft 500 )
/// Micke

Almost, 749 or 999.
The standard butterfly diameter is 54 mm, but it can be bored to 58.
Micke; Do you know if he bored them out?

[AJ]

Micke, do you know what he is running for throttle bodies?

Thanks,
Will

Yes
DUCATI 749/996     ( EFI fultech Ft 500 )
/// Micke

Almost, 749 or 999.
The standard butterfly diameter is 54 mm, but it can be bored to 58.
Micke; Do you know if he bored them out?

Yes I did bored them out, I did some cerful messurments and came to the conclusion the they can only be bored out to 56mm to retain some strength as the body has a smal taper.
As to what power you can get out of a pair of 51.5 IDAs I would say 290 at the crank at the max, more than that, and you have to be a magician imo.

[hotstreetvw]

Excellent.  I'm not a magician, so the 285 is solid until I can move to FI.

This thread brought to you buy Kleenex tissues, for when the dyno doesn't give you the number you're looking for.

[modnrod]

You guys are making 4 times as much power as I am! Hahaha!

On my bikes however, I have noticed exactly the same thing where the apparent reversion causes a flat top end. I have always fixed it by changing the stack length to vary the WOT tuned length.
On my street bike recently I ADDED stack length, which theoretically tunes the torque curve lower, but also richens up the top end. The ECU is tuned around AFR map using a O2-sensor (Triumph), but with no mapping or changes I went from 121mph to 127mph in the same conditions.

Tuned length is a lot cheaper than throwing the carbs in the bin!