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[75evo]

JK,

Are the ITBs going on this car? BTW, wouldn't it be more cost effective to have twin plenums and 2 smaller throttles?

Ferrari ditched ITBs and used twin plenums. The last V8 to have ITBs was the F355. So I'm questioning the benefit of them

I was wondering if we can pair the cylinders up in pairs of 3, just like how exhaust headers on an inline 4 are paired up according to their firing order to help scavenging.

You can use modified 164 plenums or custom make your own. Although custom plenum may defeat the cost savings from ITBs.

Only other issue is from what I have heard, ITBs are a pain and a half to tune.

Thoughts?

[Greg Gordon]

Why would twin throttles help? As long as the manifold pressure is at or very close to ambient when the throttle is fully open, more throttles won't add any power. I haven't worked on any Ferraris, but I suspect they dumped ITBs because they have become a lot less important with the advent of variable cam timing, something that's not a factor here.

Greg

[MD]

I am presuming we are discussing plenums Vs ITB's for road application only?

[Duk]

Mats's video of a manifold simulation speaks volumes for what can be happening inside an inlet plenum chamber. Simply calling a plenum chamber's behavior based on pressure drop is like claim 2 cars handle the same because they have the same tyre's.

Flow bias, the way air will naturally go with the least resistance to flow is very important. Sharp, unforced turns are bad and sharp turns in 2 different directions are worse.
Looking at a 164 plenum, I'd suggest that numbers 4, 5 and 6 would be the better performing of the 6, in real world use.

Then there is the potential for robbing of air in adjacent runners, like what Mats video shows. It particularly bad for performance if the air that is robbed from 1 cylinders runner is the next in the induction stroke order.

I think the best real world testing could be done by logging the exhaust gas temperature in all 6 extractor pipes, as close to the heads as possible. This is of course assuming that all 6 of the extractors pipes behave the same (all 6 equal length and equal entry angle into the collectors).

[Greg Gordon]

Mats's video of a manifold simulation speaks volumes for what can be happening inside an inlet plenum chamber. Simply calling a plenum chamber's behavior based on pressure drop is like claim 2 cars handle the same because they have the same tyre's.

Duk, I am not sure if this post was in response to mine, but just in case it was... I was addressing the issue of ITBs as raised by 75evo. I said nothing about plenum design. These are two different things. For example you could put the stock runner and intake plenum on top of ITBs and remove the stock throttle. That would give you ITBs with the exact same plenum. Not that anyone would do that, but the point is ITBs and the plenum are two different things.

Greg,
http://www.hiperformancestore.com
http://www.okinjectors.com

[Mats]

JK,

Are the ITBs going on this car? BTW, wouldn't it be more cost effective to have twin plenums and 2 smaller throttles?

Ferrari ditched ITBs and used twin plenums. The last V8 to have ITBs was the F355. So I'm questioning the benefit of them

Thoughts?

1. Electric Throttlebodies, two of them.
Easy to make the engine put out exactly the amount of torque the EMS (Engine Management System) allows. Anti-spin, ESC and that.

2. Emission
Wild cams needs ITBs to keep the EGR in check during overrun. Since you can get power without those insane cams nowadays and you need E-Throttle to get the tip-in/tip-out and such for emission the ITBs are pretty much obsolete.

It's not like the power is going to be different at WOT anyway.

[Greg Gordon]

It's not like the power is going to be different at WOT anyway.

Yeah, what Mats said. ITBs provide no advantage at wide open throttle, thus have no positive effect on power. There are times when ITBs are great, for example on a car with really hot cams they help idle characteristics.

Greg Gordon,
www.hiperformancestore.com
www.okinjectors.com

[75evo]

What about throttle reponse? I wonder if you lose the sharpness with an oversized single throttle as opposed to ITBs. But with good EMS programming you could probably get a big throttle with good response, just my guess.

I think i will try to just improve th plenum outlet to the runners, bell mouth it properly, and maybe increase the volume a little. ITBs seem to be unnecessaary for my race car since i dont care about idle quality. And lots of people whom I have spoken to say syncing up and tuning ITBs is a headache and a half, more unneeded work.

Ithink JK didmention his intention for ITBs for his future 3.2. Maybe because his is a road car and idle quality needs to be at least acceptable with big cams.

[SydneyJules]

Interesting conversation going on here.

I've experienced 2 cars with aftermarket ITBs- one was a Datsun 240z with a hot NA engine and the other was a Holden gemini with a 2.6 Isuzu four cylinder out of a Rodeo ute (pickup)- this Gemini had 12:1 comp and ran 12.9s naturally aspirated. It revved to 9k and was regularly street driven. I don't know about the datsun- he injected it from the start, but it pulled very cleanly from idle. ECU was a Haltech E11v2 (part of the reason I bought one- something I may live to regret, not sure yet).
The guy who owned the Gemini said that the change to ITBs from a singlethrottle/plenum gave him so much more torque and made the throttle response much sharper, that he stopped trailering the car to the drag strip and started driving it on the street.

The tuning isn't too hard from what I've heard, but a pedal box is mandatory due to lack of vacuum.

So, the ITB thing may be obsolete on a modern super car, but I think for us into older-skool motors chasing NA power, it's the only way we can guarantee proper breathing.

After talking to Vin Sharp, I'm convinced that an ITB setup will give me more everywhere in the rpm range- as soon as the interference of the various waves in the inlet were explained to me, as a function of cam lobe profile, it sounded exactly how my engine behaves at low-mid rpm. Greg is right on the idle front, but I think there's a fair bit to be had in the midrange and up top too, which is partially in the runner length and trumpet length.

It's got to be akin to breathing through a straw with a single throttle and long pipework coming off the plenum into a filter, right?

My BMW mates with their tube frame 2002 Sports Sedan ran the car as an NA 2.0 with F1 head and F1 titanium rods revving to 11k NA before they went turbo, and said it took a few goes at runner lengths before they settled on the best spread of top end/mid range. I don't really wanna be spending all that $ tinkering with things over and over, so if anyone has a set of jenvey throttles, I'd love a measurement!

Are you gonna go ITB Jim?

[Jim K]

ITB's are my intention for the future 3.2liter -if it ever happens that is, given our well-known financial conditions! Right now, I'll have to see how good the existing 3liter can get after mapping the oem management. I still have to work out some annoying electrical gremlins (warning lights) but the engine runs very well -has ~700km now. Yesterday, I hooked the wideband on and saw 11.8-15.6:1 across the board -took it up to 7krpm where I've set the shift light. I replaced the N2C plugs with BR8ES and got rid of interference induced backfires. Tomorrow I'm putting in PFR7B plugs. Although performance seems reasonable for a fresh engine, driving the car hard, I get the impression something is holding it back; the need for mapping or the very few break-in kms. I'll remind you of what has been done:
CR is 11.3:1
Renault Williams 2liter cams, 9.8mm, 216*@1.25mm (std is 9.3mm, 208*@1.25mm)
Limited porting
Cearances of 0.045/0.06mm (main/rods)
Everything balanced
I'm hoping to install the oil cooler tomorrow, with the thermostatic sandwich plate.
Jim K.

[Mats]

It's got to be akin to breathing through a straw with a single throttle and long pipework coming off the plenum into a filter, right?

Not really, unless you have a 2" pipe doing ten 90* bends or something.
You can however fark things upp immensly if you screw up the secondary tuning of the said pipe... How do you calculate that you might wonder? Well unless you know how to use GT-Power or similar software you will have to try several pipes to see what works.
Or just make it short/wide enough to not work as a resonator.

If you are looking to get a more progressive opening on a large single TB you can always add "lumps" on the butterfly to make the opening between the plate and wall grow at a more reasonable pace. Easy to tune as well if tou make the lumps out of alu or similarly soft material.

[SydneyJules]

very interesting Mats.... I may re-vist this at some stage in the near future- I've had to remove my airbox temporarily, and don't think I'll be putting it back in (The Zender bonnet hump will have its holes cut out and I'm going to run a short pipe and filter up there)- then I'll look at Gsxr throttles like MD

Jim, how many Ks has the engine travelled?

Will you be going to Jenveys or making your own?

[Jim K]

The engine has ~700km now. I can still feel it 'tight' when loading it in 3rd/4th. I'll take a long trip in a couple of weeks, ~1200km and then if all is still well, I'll map/dyno. Today I finished installing the oil cooler. I'm still messing with minor issues like trying to calibrate the water/oil gauges. Its a stupid time-consuming chore but eventually, I'll be able to trust my gauges -I always go through this with my cars.
Jenvey is too expensive. We have some guys here making such things and supposedly they are working on a 24v set; I gave them a wooden mockup with the two short 'manifolds' bolted in place. They can use it to design their ITB's. If this doesn't work, I'll yell 'Kevin, are you there?' and see if anyone answers! At any rate, this is (sadly) more a financial issue than a technical one for me.
Jim K.

[75evo]

"supposedly they are working on a 24v set"

This is starting to sound like "big bore headers for the 12V coming soon"

[Jim K]

Don't know how they're doing; they're ~80km from here and I'm not really itching for ITB's right now, hence the lack of urge to investigate.
Big-bore headers? There's only one set around that I know of and its in my 12v 3liter -half sold, as I've only been paid half the money so far! And yes, they unfortunately did cost a $hitload...
Jim K.