intake runner lenght with ITBs discussion

[jondee86]

Jimmi The Kid Wrote:I will place my injectors at the end of the stack - oldschool formula 1 trick...

I have looked at mounting injectors at the mouth of the stack, because
of the more efficient fuel vapourisation. Obviously it works well for any
kind of racing where the throttles are wide open most of the time.

However, my research indicated that there are some drawbacks when
using this system for a car driven on the road. It seems that having the
fuel on the "wrong" side of the throttle butterfly is not so good for idling
and low throttle opening. And probably cold starting will also be difficult.

I'd be most interested to hear from anyone who is using this system on
their road car... and not just as secondary injectors that only come into
action at WOT !!!

Cheers... jondee86

[NoHachi]

I can offer some experiences from a race car... Unless you like fires, don't run your primary injectors before the butterfly.... Even at high rpm/VE, suddenly closing the butterfly during an injection event will send clouds of petrol fumes into the engine bay/plenum... Never mind what happens with hot cams and low rpm/open throttle. Air is streaming in nearly all directions then..

Don't have video of the explosions, but might have a picture of some nice exploded carbon plenums.. had to rebuild 4 or five of em before I realised I had the injectorbanks switched.

[Jimmi The Kid]

If you run with the 20v ITB's on a 16v, you dont have a idlemotor as the Silver or Blacktop have. Then you have to open the throttle a bit, to idle the engine. So the throttle will never be fully closed, and then it should suck in all the gasoline. Or am I wrong???

[NoHachi]

Ghe ghe, try it without a plenum on and you'll see what happens soon enough. Just make sure to have a fire extinguisher nearby

No biggy though, just keep the stock injectors as the primaries and add the second injector bank. Most ecu's will happily run a second bank. That way you get to keep small injectors and accurate low power injecting. Whatever you do, don't move the injectors and use the stock ecu. Sequential timing will be way off.

ps an engine is not "sucking" all the time. With hot cams they can blow too. See e.g. Carbs backfiring.

[jondee86]

NoHachi Wrote:ps an engine is not "sucking" all the time. With hot cams they can blow
too. See e.g. Carbs backfiring.

Yes, I have seen the effects of reversion and fuel standoff with carbs and
injectors close to the head. I can imagine that with injectors at the mouth
of the stacks, the problem becomes greater. Would look awesome in the
dark

Cheers... jondee86

[eight-six]

Bean – sounds like your going for some long stacks – might be worth checking they will fit. I have 75mm stacks on my OER ITB’s and they are literally right up against the inner wing, which cant be good for performance. I have decided to reduce the length of mine - IIRC 45mm. I couldn’t find any to fit my throttles without paying bum rape prices so started to make my own.

How long the stacks are …



My trimmed down FRP version … trying to source some carbon or carbon Kevlar to make the final version. This one was just a test.

Quote:The more usual materials for thermal insulators are "Phenolic" sheet (a fabric reinforced plastic similar to Tufnol) and the more expensive, but better performing "Teflon" sheet (virgin PTFE). I have an insulator water jet cut from 3.1 mm Teflon, but the engine has not run yet, so I cannot comment on the performance.

Do you need to bother with Phenolic insulator on ITB’s? Was under the impression this was a Carb thing, and the idea was to insulate the Carb from heat transferred through the engine, obviously the heat could cause issues with jetting / floats etc.

Cant see the point in doing it on a set of ITB’s or even with a conventional inlet plenum. The air will flow so quickly through the stacks / plenum the chance of a hot plenum heating the air is going to be very small – I would assume the plenum would need to be red hot for it to even come close to affecting the incoming charge temperature?

[Bean]

cheers for your input eigth-six my priliminary measurements should allow thos lenght of stack without issues as my car is LHD I have more space on the intake side because the brakebooster is on the exhauside... but I'll be fitting everything step by step to avoid problems like these.
How hard is it to make the stacks yourself as I plan to build a custom airbox anyway I though about the stacks too just not too sure about diong them myself as they are a bit more complicated to do compared to the airbox and I don't have any experience with creating fibre parts yet...
due to life beeing a bitch I wont be able to start my final build until late summer so plenty of time to learn and practices some stuff I'll need to create.

[Jimmi The Kid]

This guy here have no injektors in the manifold, and no fireextinguisher
He claim that the engine puts out 200hp with 304' TODA cams, stock pistons, AE111 con.rods, modifyed smallport head, weld on intake manifold, AE101 ITB's.

[Bean]

200hp is absolutly doable... two of my frined which particiapate in hillclibing have 200-230hp 4A-GE (bigport 16V with custom cams and other bits and bobs)

[jondee86]

Here are a few people chatting about fuel reversion and standoff... not
technical, but illustrating the potential problem.

http://www.shoptalkforums.net/viewtopic....&view=next

If the engine bay is bare (as in most race cars) and you don't have any
easily ignited material, the odd burst of flame probably won't do any harm.

Phenolic spacers reduce the rate of heat transfer from the head to the
intake manifold. This will give a cooler manifold, and reduce the rate of
heat transfer to the incoming charge.

I have never seen the performance benefit actually measured, but the
physics is good. Raising inlet air temperature from 20 to 40 deg C will
result in 3.5% loss in power. So the spacer can reduce the air temp by
even 5 deg, that's one more hp My spacer replaces the OEM gasket.

Stack length is always an issue in RHD cars. This is what I had to do
with mine (excuse the temporary wiring)...



Cheers... jondee86