Q's about ram horn injectors

[bill mcdonald]

I have been wondering how good of a design are having those injectors mounted there?

it seems like it would cause uneven fuel delivery to the cylinders, and when you let off the throttle fuel would semi puddle on the throttle body blades?

I suppose the more time fuel has to be suspended in the compressed air the more cooling it could do to intake temps?

I am just wondering how it works out.
Anyone have any issues with it?

What is actually holdeing the injectors in the ram horns? I never seen one up close. it appears like they are just resting there.

Anyone care to point out any more advantages or disadvantages to the design?

 

[*89x2*]

I think it is a great design to overcome the packaging constraints, while providing the needed fuel under pressure (boost).

Sure, designs have come a long way and we are seeing some cars fitted with larger injectors (only 8 of them) and also a 16 injector set-up has been spotted a time or two :cool

I have had no issues with mine at the rams horn end, just make certain the "T" fitting is snug on the rail, or you might find a fuel drip...
System works off of boost, it will "turn off" once it is back out of pressure :cool

 

[Aurora40]

I'm no Callaway expert. But the injectors are probably a bit different than the normal injector. I'd bet they either fire more rapidly, or are constantly on (when needed) to feed all cylinders. It shouldn't be uneven as it is so far up the airstream.

It also shouldn't puddle up. Even at idle the engine is sucking air, and I believe the injectors only come on in high-demand situations. The stock injectors could probably handle part-throttle situations.

I would guess it was easier to add the extra injectors and controller than to add larger injectors and change the stock controller. Or perhaps the controller wasn't capable enough to handle so many variables (computers in 1987 weren't what they are today). Or maybe large injectors wouldn't be precise enough for off-boost situations or something.

Just guesses, though.

Are there wastegates or blow-offs on the turbos?

 

[SurfnSun]

In the search for "serious" power, you'd want to stay away from the front fire injectors. Put too much boost thru there and all the gas will end up at the back of the plenum.

 

[EricVonHa]

Though the fuel passes directly over the throttle butterflys-- the turbulence is always enough to pull the fuel past into the intake and down into the manifold. Have no fear about the fuel puddling up on the throttle butterflys... the injectors are driven via a separate controller that is boost and rpm sensitive. The "Microfueler" controller will only pulse the injectors when the motor is under boost. Even if you quickly spool the turbos up and let off the gas, the fuel won't puddle. Any of these EFI throttle body cars are never fully closed even at 0% throttle. Try taking the throttle body air bridge (or maf) out of the picture on a standard EFI sbc and start the car. There is still a tremendous amount of air passing by the throttle blades just to keep the car idling. If there is any fuel mist there-- it's gone in a hurry!

I've never put a scope on the wiring harness to the injectors (thankfully mine has been error free). However, there is a DC light bulb that Callaway has listed in their technical literature for troubleshooting Microfueler issues. If the light bulbs flicker or come on under simulated boost and rpm signals then the electronics is a-ok.

The design placement of the supplementary injectors is fine for "standard" horsepower applications. Leaning out the #1 and #4 cylinders has been an issue for high revving, high hp small blocks in a similar configuration... but not within the realm that the Callaway motors were built. Carroll Supercharging has a similar design for their supplementary fuel injector setup and I've heard that the front 2 cylinders run slightly leaner on mega hp motors. However, the Callaway setup was tested for ultimate streetability with a factory backed GM warranty so it's not even an issue in design or long term spirited use.

 

[Aurora40]

In the search for "serious" power, you'd want to stay away from the front fire injectors. Put too much boost thru there and all the gas will end up at the back of the plenum.

Why would that happen?

 

[SurfnSun]

Well say youre boosting the 20psi... the faster and harder the boost comes thru the throttle body the farther its going to carry the gas, by passing the first cylinders as Eric stated in his post.

Lets say youve got a fan blowing at 40mph and you dump water in from above...it will take the water XX feet. Now crank the fan to 65mph and dump the same water in...how much farther will it go.

 

[EricVonHa]

Uh, Mr. VonHa... the front two cylinders in a sbc are "1" and "2"... .not "4"..

 

[Aurora40]

Well say youre boosting the 20psi... the faster and harder the boost comes thru the throttle body the farther its going to carry the gas, by passing the first cylinders as Eric stated in his post.

Lets say youve got a fan blowing at 40mph and you dump water in from above...it will take the water XX feet. Now crank the fan to 65mph and dump the same water in...how much farther will it go.

But that isn't what happens in an engine. The cylinders would be actively pulling the air and fuel into them. Otherwise, from what you are saying, the front cylinders would get deprived of any air also as it would all just blow past them.

The turbos are really pressurizing the air in the intake, not blowing it through it. If the turbos were running and the engine was not, the air probably wouldn't move around a whole lot in the intake, it would just get compressed more and more until the turbos could no longer compress it. It's the cylinders that are sweeping back and creating a new area for this compressed air to move into that cause the air to rush through the intake, and this happens as much at the front of the intake as it does at the back.

I'd think it would be more likely that the back cylinders would be the most likely to get fuel starved from a front-mounted injector.

But I'm just speculating. Are there any instances of high-output Callaways where what you described happened? Did the Sledgehammer have the same extra two injectors up in front of the throttlebody?

 

[8388]

The set up is simple, because they always intended the cars to have all of the same drivability manners of the regular vette, and so long as the intake configuration remained the same with the same rev capabilities, the two external injectors are more than adequate. This set up allowed Callaway to run off the same basic fuel and timming map as the non turbo vettes. If they had chosen to go with eight larger injectors, they would've had to remap the entire program and that in itself would have required hundreds of test and tunning hours.

 

[SurfnSun]

Ok perhaps my anaolgy was a bit off...I understand the concept of a pressurized intake. Im just passing along the info given to me by a couple of Callaway and turbo gurus. I believe this has been verified by EGT testing, though I do know of one car that is boosting high with out the problem. There was one car which they couldn't run over 15psi b/c of this type of problem.

The sledge did not use supplimental injectors...nor did the 89-010 car.

Sorry E, I read your post too quickly.

 

[Peer81]

Thanks for answering the question i wanted to ask Josh!
If i heard correctly for the shop that checked the #010 the ECM had about 2x the capabilitie's as a normal corvette ECM. Would that be the answer to the missing pre injectors?

And do the Super Speedsters have supplimental injectors?

Groeten Peter.

 

[*89x2*]

And do the Super Speedsters have supplimental injectors?

Groeten Peter.

SuperSpeedsters use 16 injectors, same as a regular Zr1

 

[SurfnSun]

If i heard correctly for the shop that checked the #010 the ECM had about 2x the capabilitie's as a normal corvette ECM. Would that be the answer to the missing pre injectors?

89-010 used an Accel DFI system to control fuel curves. The factory ECM was left in place to control everything else in the car, not fuel related.

 

[Peer81]

Thanks for the info Josh!

Groeten Peter.

 

[Crosschkm]

Does anyone have info on removal and re installation of the injectors on the Ram Horns? I want to clean up my ram horns, it looks simple but do I need to be aware of anything?


Cross

 

[malc350]

Yep, if tou have the Callaway manual that came with the car make sure you read the part where it tell you how to remove the ram's horn.

It is VERY important to hold the bar by placing a spanner in the "flat" paret of the bar, then "crack" the bolt open to remove the fuel line. Also make sure the line going to this bar doesn't get caught and is routed correctly if you're doing something like taking the intake off - other wise you may find the line doesn't reach!

Make sure you don't lose the rubber gasket between the throttle body and the ram's horn and that it is refitted correctly.