Hey all,

I realise that this may have been hammered at before, but I was currious if, on a stock 2.0L, there was any distinct advantage of going to IR throttles over the stock plenum (or some other single throttle plenum).

I know that the stock cam will limit the amount of air the engine can ingest, and that IR throttles will definitely NOT be the limiting factor on the top end, but with tall manifolds, and IR throttles, can a stock 2.0L run better than it could with the stock intake plenum. Assuming that both are running a programable fuel injection system that has been optimized.

Thought? Experiences? Test data? Dyno results?

-Josh2

Pure speculation and second guessing:

Several people who should know have stated that the stock 2.0 plenum setup is good for lots more than the stock 2.0 puts out, so a "stock 2.0" almost certainly won't benefit from changing the induction system. The numbers that get bandied about are 160-180hp is the upper limit for the stock setup. Dave Hunt is using the stock 2.0 plenum on a Raby 2270, and even Jake hinted that the stock setup would be, at worst, "marginal".

Now, if you're planning on changing the cam, and doing some headwork, and using an aftermarket exhaust, that's when you have to start worrying about the stock plenum setup.

From everything I've been able to glean, IR setups are primarily about throttle response (i.e., reducing the "throttled volume"), not about absolute flow. Plenum systems have the advantage of being easier to work with (no throttle synchronizing, easy to tap a steady manifold pressure signal, easy to make up efficient filtering for), but out of necessity have a fairly large volume between the throttle plate in the valves.

Cool.

So, distilling this question a little more: If the target was a car built for competition (and no cams, the rules require stock motor internals), is there an advantage to running IR throttles or plenum?

If there's a top-end for mid-range trade off, it's maybe not worth it, but I'd like to get some ideas going here...

Thanks!

-Josh2

Josh

You say stock internals but, you didn't mention whether you would try to use D-jet or another system. I can't see D-jet working so I'm going to assume some other system.

I would have a hard time seeing much advantage with IR without internal changes. Throttle respose on the stock system is pretty good so no gain there.
I just have to believe that the cam is the primary thing holding things back.

Dave

Yup, stock internals, but everything else (short of turbo-charging) is unrestricted. Kindof the opposite of production cars...

Already have the headers, and the stub pipes have already been matched to the heads.

So yeah, I'd be going with a programable FI system either way. I have hardware at my disposal for IR throttles, I also have a complete D-jet intake setup. The questions is, is it worth it at all to even try IR throttles or just stick with the D-Jet plennum?

-Josh2

Definately the cam would hold you back as its setup so mild I don't imagine IR TB's would work very well or atleast be a pos to tune.

If you can, work on the valves, springs, lifters, pushrods to get more outta that end to get more hp and revs

QUOTE (Bleyseng @ Jan 17 2006, 05:05 PM)

Definately the cam would hold you back as its setup so mild I don't imagine IR TB's would work very well or atleast be a pos to tune. If you can, work on the valves, springs, lifters, pushrods to get more outta that end to get more hp and revs

Geoff,

Not much I -can- do inside the motor... Like I said, stock internals...

It's sounding more and more like the IR throttle idea is only gonna yield positive results with a hot motor... that's not an option....

Anyone else? Jake?

-Josh2

atleast better valve springs?

valve stem keepers?

I did this test in October. On a 2270 "Daily Driver" combo the plenum was "Sufficient" for the powerband of that engine combination. I swapped it to a pair of 45mm TWM Throttle bodies and the engine made more power, and did increase efficiency (BSFC#s logged) and gained HP by 5% due to added RPM. Torque was boosted by near 10% at peak.

The same test was done in December with a bit more dense air on a 2270cc "Performer" combination. The results proved that the plenum was absolutely maxxed out as the individual runners made a solid 20% more power than the plenum did on the same engine- the plenum also required altered ignition timing to retain the optimum power numbers, something that was not a characteristic of the "Daily Driver" combo and certainly not conventional.

remember that plenum systems are seriously impacted by camshaft and vacuum signal dictated by the cam. This is the magical part of the combination (and between the Daily driver and Performer combos) that separates the men from the boys with designing an engine for a plenum, or Ind. runners- totally different schools of thought must be used to build each engine the best it can be.

Based upon what I have seen so far, the stock plenum is dead after 155HP, BUT it's "All in the combo"

Anyone serious about making a plenum based system work the best of it's ability is not very wise if they don't consult with me and use one of my cams to get the job done- period.

Josh
For what you are needing, IR will be much better. The constant changes in throttle position will require a system that reacts very quickly. LIghtened flywheel, clutch, fan. etc will help the engine rev much faster in addition to the TBs. A plenum system will have some inherent lag in relation to throttle position as the column of air that has to stop and start is much bigger with the plenum setup.

I would have a set of the shortest manifolds you can find, attached to the engine and tune the exhaust system accordingly. This would be a very strong combination for autocross.


In all situations transient response is much more important than maximum HP. the faster you can recover from a shift or change in throttle position the faster your car will be. In an autocross you have a minute maybe two and have very little room for error. The better your engine recovers the more likely you will win or can correct a slight error that might eliminate you from the finals.

However, the original point was that the cam could NOT be changed. Stock has to be used. So, with an internally stock 2.0, having nothing more than a header on it, would the TWM throttle bodies do any good? Is the stock plenum good enough for this?

Yes, IR will have it over the stock plenum. Measure the distance from the valve to the throttle plates. Now measure the distance from the throttle plates on a IR setup and you will see the reason why IR will be the best for his application.

I thought that only mattered at wide open throttle. I thought one of the benefits of a plenum was the other cylinders were keeping the air flow into the plenum so it is "forced into" past the valve some. You don't get that with IR so you lose some torque.

QUOTE (jhadler @ Jan 17 2006, 03:10 PM)

there was any distinct advantage of going to IR throttles over the stock plenum (or some other single throttle plenum).

what's IR

"Independent runners"?

QUOTE (Bleyseng @ Jan 17 2006, 07:19 PM)

I thought that only mattered at wide open throttle. I thought one of the benefits of a plenum was the other cylinders were keeping the air flow into the plenum so it is "forced into" past the valve some. You don't get that with IR so you lose some torque.

Right, but there's the other side of it too...

With an IR setup, you develop a "stack" of air fuel mixture above the intake valve before it opens (the injector has sprayed two squirts of fuel into the manifold), and the air has a straight shot down to the valve instead of having to turn throgh the manifold. Gravity assist if you will...

I really don't know however if the IR is any better than the plenum with a STOCK motor.

Jake, I have no doubt that the IR setep is better with a hot motor and more aggressive cam. My question is regarding a stock motor with a stock cam.

The plenum intake can generate intake pulses that can help draw in more air, but the IR can drive it into the combustion chamber better. So, what's better with the weak-ass stock cam in the 2.0L motor?

So, given that, will an IR intake be any better than a plenum under those conditions?

-Josh2

QUOTE

Jake, I have no doubt that the IR setep is better with a hot motor and more aggressive cam. My question is regarding a stock motor with a stock cam

Can't help you there.....

Stock cams are against my religon!

I agree with Brett that throttle response will be better with an IR setup and tunable fuel injection, compared to the stock plenum and the same fuel injection system. Peak torque and HP won't be significantly improved however, and I doubt you would "feel" much difference between the two.

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.

So what happened to Muellers IR setup that he was building? That would be a good test mule.

I'm also with Brett, based on my findings.

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

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.

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.

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.

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

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

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

ask and you shall recieve



mickey mouse engineering Motorcyle TB's to a type IV

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

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.

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

How about we all just get old 911 motors with MFI

BTDT... Love the sound and the performance!!!!!


Gas mileage sux though!

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

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!