Thread: NEWs about 43mm ITBS VS N1 TB

Hello, Who can explain this?

You guys have seen my dyno sheets with 43mm itbs and with N1 tb. N1 have more hp and holds power at more RPM but check this...

we now N1 give better dyno sheets but when its about racing on the circuit... mmmm (dont know what to think).


With 43mm ITBS lap time 1.05.80 (with old dry used tires 1.06.00)
With N1 TB lap time 1.06.40

Diference is less than 1 second BUT ITS ALOT FOR RACING.


Tested on Same car, same Engine, same setting, new tires, same fuel.

Now I am thinking on going bigger ITBS 50mm or 52mm maby dont know yet... with a nice custome manifold for them.

Your power could be peaking early because of the length of the ITB's. They look longer than the factory intake manifold runners.

itb will give much better throttle responce that can help at the track.

Also those runners look really long. And the air box looks small.

Also the peak power diff of the itbs vs n1's was not that much, less than 5whp. The itb's peaked 1000rpm earlier. Depends on where you spend your time in the powerband.

Also black top 20v 4age's are 45mm i think. Its the silver tops that are smaller.

In my opinion, I would do a few more runs and get used to the new power band. It may just be getting used to a new power curve and shifting at different points on the track to keep it in the new powerband. Just my guess though. I don't see how throttle response could make up for those number differences at all.

Maybe the conditions of the two days on the track can also account for some... some of this. I know my car will run 3 tenths of a second slower in the 1/4 from a little humidity.. these were two track days back to back.. zero changes.

A diffrent power band needs diffrent driving style aproach.


Cory the track days were not back to back. I am sure the temp was diffrent also.

The trck days were back to back. I went there set the car up and ran 6 consecutive 12.0s and then the car sat at the track over night, and the next day with just weather being diff gained 2-3 tenths and 2-3mph with no variables...

we are talking about his car not yours Cory.

His track days were not back to back when testing the ITBs against N1 TB/

Saca Chispas, do you have dyno sheets for each setup you can post for us to look at? From what I've read it seems like you had more area under the curve with the ITB setup (even though you had less peak power). Can you confirm that? Because that, coupled with the throttle response could have made all the difference.

I'm also getting the feeling from other posters that the intake manifold you used with the N1 TB isn't similar to the ITB setup so there might be room to grow there. Do you have pictures for us who haven't been following your build?