ITB's with a twist

[wondersparrow]

Has anyone here converted from triple Webers to the extrudabody ITPs and measured the performace before and after? I was wondering if there is much of a performance gain to be had, or just the consistency and programability of EFI. I have triple Weber 45 DCOEs on my L24 and was considering doing something like this in the future. I want to have a spare engine ready to transplant into my roadcourse car the second it gives me issues. EFI/ITBs seems like a good way to go.

[Accurate Injection]

Unfortunately we have never done a Back to Back Test like that yet, we are working on a similar test on the BMW 2.5ltr I6!

 

Only thing I can say is it will depend greatly on the size of the Weber Chokes used in that test, and the size of the Weber throttle shafts compared to the 6mm cross section of the Extrudabody throttle shafts that improve flow potential!

 

Kevin

[Tony D]

Has anyone here converted from triple Webers to the extrudabody ITPs and measured the performace before and after?

Not on the extrudabodies, but on TWM 45mm ITB's...which functionally should be equivalent.

 

It expanded our power peak around 800 rpm upwards. There was a 17 HP difference at the old power peak in the ITB's advantage, and 40HP at the new power peak.

 

Same engine, same cam, simply replacing a distributor and Weber 45 DCOE's with TWM 45mm ITB's and a TEC2 EFI system.

 

Basically this is the same power level we expected had we gone with the 55 Webers the engine builder said 'were the next step'...

 

Ever price a set of 55 Webers? The ITB's were cheaper!

 

But that was not the half of the improvement. With carbs the engine idled at 1700 rpms, and roughly at that. And cold starting was not a simple matter...especially at 39F on November Mornings.

 

With the EFI, we could take the exact same engine, and with a twist of the key start it at 39F, have it go to fast idle at 1800, and slowly work it's way down to an 1100 rpm idle. We actually screwed around with the IAC circuit and idle bypasses and were amazed with the ITB's in place (and owing to E-Motive's PAFFZ-Blend Software) we could actually idle the engine down as low as 450rpms!!!! Simply amazing and like night and day.

 

The power to be had is only part of the picture. Sure, we picked up 40HP at our new rpm. That's on a stout motor. What we got was OEM Twist-Key reliability to start and drive a monster engine without pops, coughs, and any cold running issues...as well a no more transitional bogs due to low manifold vacuum, etc etc etc...

 

If you are daily driving the car and have properly jetted and sorted carbs, that is where the difference will be...that and fuel mileage. If it's WOT, I'd liken it to what we did going from 45DCOEs to 45ITB's---equivalent to the next largest competitive carburettor. Frankly, we could have made half that ammount going SMALLER in ITB diameter and running 40's instead of 45's and STILL had all the advantages. For a street car, if you have 45 DCOE's you could easily go down a size and STILL gain power, but have better velocity and MAP signal, as well as drivability from the decreased tip-in response.

 

It all depends on what you want. Power is really not that big an issue, the drivability, especially cold, is!

[Accurate Injection]

http://www.extrudabody.com/TechInfo/FlowInfo.html

 

The Link above is a Direct Comparison done by an independent Flow Bench testing facility, that compared the Extrudabody 40mm to TWM 40mm, and the 216.1cfm for Extrudabody to TWM's 206.1cfm speaks for itself!

 

The L28 testbed we used with the Extrudabody ITB's was indeed 45mm DCOE as well.

 

Kevin

[wondersparrow]

Of course the improved fuel management will acount for a lot. I dont know what size the throttle shafts are, but I am pretty sure I have 38mm chokes in there. I don't know what the limitations of these heads are when it comes to flow, but somehow I don't see anything bigger than a 45mm ITB working well on an N/A setup. I do like the looks of the secondary injector mounts though.