IR vs. Plenum?, Bonafide dyno tests anyone? Options

[jhadler]

Okay,

Based on the input from some rather experienced and talented chaps here, I'm gonna stick with the plan of developing the IR throttle setup. Probably gonna use Megasquirt.

I'll be setting the car up first with the stock D-Jet, just so I can get the darn thing going. Once the car is on it's wheels again, I'll start the buildup of the MS hardware.

Thanks all!

I suspected the IR setup would be better, but not by much with a stock motor...

-Josh2

[eeyore]

QUOTE (Brett W @ Jan 18 2006, 06:41 AM)

Build a high butterfly injection system and you will pick up about 10% over a standard below butterfly system. If you are using a decent FI system, I would build a staged injector setup and really increase the torque curve.

That sounds great! I wish I knew what it meant. (IMG:http://www.914world.com/bbs2/html/emoticons/blink.gif)

[lapuwali]

QUOTE (Cloudbuster @ Jan 18 2006, 09:40 AM)

QUOTE (Brett W @ Jan 18 2006, 06:41 AM) Build a high butterfly injection system and you will pick up about 10% over a standard below butterfly system.  If you are using a decent FI system, I would build a staged injector setup and really increase the torque curve. That sounds great! I wish I knew what it meant. (IMG:http://www.914world.com/bbs2/html/emoticons/blink.gif)

It means that the injectors should be mounted high, above the throttles, rather than down low near the valves, as they are on most OEM EFI systems (including the stock D-Jet). The idea is that you're allowing more time for fuel vaporization, esp. at high revs. The low mounted system works better for part-throttle drivability and idle quality, which are important for a street car, but not so important for a track car. The favored location for the high-mount injectors is above the mouths of the intake trumpets, pointing straight into them. If you use TWM throttle bodies and the usual K&N filter setup, you could probably mount the upper injectors in the top filter plate. Indeed, a cheap way to get an IR setup is just to use a set of used IDFs, pull out the venturis, and the aux venturies, mount the injectors high, and there you are. Very little fabrication involved, and much cheaper than a set of TWM throttle bodies.

Staged injection means you use more than one injector per cylinder, so you get better "bandwidth" from the injectors, using just one set for low-speed operation, and both sets for high speed operation. This would improve drivability, and if you mount one set of injectors high and one set low, you get the best of both systems. Megasquirt will do staged injection, at least with the "extra" code.

[jhadler]

I dunno if staged injection would make one whit of difference on a low revving stock motor though. I think even the stock injectors have more than enough "bandwidth" to handle a stock 2.0L motor or more. Staged injection makes sense for a high revving race motor though, where you run the injectors near minimum durration at idle, but start to get close to maxed out at full revs. I seriously doubt that's a risk with a stock motor that is severely cam limited...

-Josh2

[JmuRiz]

QUOTE (lapuwali @ Jan 18 2006, 10:02 AM)

It means that the injectors should be mounted high, above the throttles, rather than down low near the valves, as they are on most OEM EFI systems (including the stock D-Jet). The idea is that you're allowing more time for fuel vaporization, esp. at high revs...The favored location for the high-mount injectors is above the mouths of the intake trumpets, pointing straight into them. If you use TWM throttle bodies and the usual K&N filter setup, you could probably mount the upper injectors in the top filter plate.

Cool info...if anyone has seen an F1 engine on the dyno, they have their injectors ABOVE the velocity stacks on the intake. Also look at the newer FI systems on sportbikes, they use the dual injectors to get decent midrange and major high RPM benefits. Might be able to use a crashed set of motorcycle TBs (throttle bodys) from a new GSXR1000 or something as the basis of a custom system. I wouldn't want to deal with the software though, yikes!

How about we all just get old 911 motors with MFI (IMG:http://www.914world.com/bbs2/html/emoticons/wink.gif)

[Mueller]

QUOTE (JmuRiz @ Jan 18 2006, 12:45 PM)

Might be able to use a crashed set of motorcycle TBs (throttle bodys) from a new GSXR1000 or something as the basis of a custom system. I wouldn't want to deal with the software though, yikes! How about we all just get old 911 motors with MFI (IMG:http://www.914world.com/bbs2/html/emoticons/wink.gif)

ask and you shall recieve (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)

(IMG:http://www.914world.com/bbs2/uploads/post-2-1116970587.jpg)

mickey mouse engineering Motorcyle TB's to a type IV (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)

been a "little" preoccupied in the last month so I have not worked on the mounting of them......

[Brett W]

Staged injectors actually came from turbo cars that have to use huge injectors. Try trying to get 1200cc injectors to idle on a 1.6 or 1.8 litre engine. If you can get it to idle at all you won't have a clean idle. But with staged injectors you can use the smaller injectors at mild throttle openings and engine loads, then bring in the big guns to supply fuel for massive levels of boost and HP.

You will see an improvement on a "low revving stock" engine with high mount butterfly throttle bodies. We saw that on some smaller restrictor engines we built to run in FSAE. You don't gain anything by turning 15-17K when you restrictor goes supersonic at 10k, so you look for anything you can to get on the low end.

[ClayPerrine]

QUOTE (JmuRiz @ Jan 18 2006, 01:45 PM)

How about we all just get old 911 motors with MFI (IMG:http://www.914world.com/bbs2/html/emoticons/wink.gif)

BTDT... Love the sound and the performance!!!!! (IMG:http://www.914world.com/bbs2/html/emoticons/driving.gif)


Gas mileage sux though!

[jhadler]

So with tall manifolds, and injectors mounted just below the butterflys... worth it?

I figured the taller manifolds would be worth going with as the goal is to play with the motor's strengths, that being mid-range grunt.

-Josh2

[Jake Raby]

I have moved injectors to 3 locations on a coupe of different engines... The power was not affected at all- BUT the injectors closer to the intake valves did give cooler head temps that were barely notable on the logger.

The TIV intake path is so odd that conventional rules just haven't applied in what I have found....

Yet again, it's all in the combo!