Itb's

[steveblade_uk]

There seems to be a lot of folks going for ITB's on the 1uz. Has anyone got any dyno plots of before and after fittment with no other changes? The reason I ask is this is complicated and expensive to do, they look the beezneez but how much HP/ torque gains over stock? Or indeed any? 8 throttles look great but wide open you still have 8 butterfly valves in the air flow. Is it worth the effort?

Now has anybody found an exotic flatslide throttle that would completely remove any restriction when wide open?

This would surely be the best solution in terms of gas flow.

Id love to see some plots to help understand where the best gains are to be found for least time effort and cost involved.

Maybe we could compile some data already in the public domain to pin point the areas best concentrated on to share with everyone. Sort of a condensed 1UZ tunning bible lol

 

[cribbj]

Slide throttles come up from time to time:
http://lextreme.com///forums/showthread.php?t=2701&highlight=slide+throttle

 

[rms]

Like this ?
http://lextreme.com//forums/showthread.php?t=6577&page=3

 

[steveblade_uk]

Some intresting stuff in that thread cribbj. Ive seen quite a few flatslide carbs on bikes in my time and I never realy thought the engineering of these was very difficult but this just shows how easy it is to form an opinon that is wrong. I take my hat off to the designers.

Id still like to see some dyno plots showing before and after ITB's. I know theres a few people running them but has anyone got some real hard data to show the advantages over a stock plenum and throttle setup.

I guess if I trawl lextreme.com its all here, its good when your pointed straight to the nitty gritty though

 

[Damien]

Only just saw this but I'm running ITB's which use the stock lower intake runners and I went from about 165rwkw to 178rwkw and midrange torque felt like it picked up substantially. Also my Soarer had already been converted to a 5 speed manual so the biggest difference is the throttle response which you wouldn't notice as much in an auto.

If you're looking for more power there are cheaper ways to get it but my intended purpose is trackdays. I've done a couple in the wet and it's so easy to balance the car on the throttle now.

If you're fitting cams to get high RPM power (ie. peak power 7k or above) then you'd be better off with a design that has a straight path to the heads (eg www.a1turbos.co.nz) as opposed to the stock runners which change direction twice. But if you do go that path then you'd also need a diff ratio of about 4.5:1 or the gearing will be all wrong. These are all the things I've found out the hard way.

For the same price as cams and ITB's you could supercharge or maybe even turbo your car and get way more torque and power but again, it depends on what your purpose is.

I've put a lot of info on my site regarding my ITB installation.

http://www.v8soarer.com/engine/index.shtml

 

[steveblade_uk]

Thanks Damien, the dyno plots are what I was intrested in along with an idea of the state of tune. The a1turbos plot was one of the main reasons I wanted to know more. Max HP figures always sound good but ploted on a graph with the torque plot overlaid gives a better Idea of whats going on. I see nice big gains at high rpm (6000 ish) but a very large hole in the torque plot at 4000rpm. I dont think I want to aim towards this kind of a tune in a fast road car. I want a big fat flat ish torque curve that has its peak in the 4/5000 rpm band. I havent decided if ITB's will offer any gain to me yet or just more complication. Ill be reading more on your site very soon.

 

[Damien]

You're spot on looking at the torque curve - this is what gives you the grin when you plant it. For what you describe you'd be better off with a supercharger like an M90 or if you want more, an M112.