Just to toss in a real-world scenario. At some point (1994MY I believe), GM changed the LT1 from batch fire to sequential fire. I'd have to guess this made a decent change to effective atomization, since the fuel has less chance to settle back out into bigger droplets.

But neither the horsepower rating, nor the EPA fuel economy rating, changed. I'm sure "better" is better... the question is probably, how much better?

 

I could see it running smoother especially at idle, etc, and I could see better emissions testing, but HP I doubt.
You can even compare a fuel injected car to a carbed car, and no doubt the fuel mileage, driveability, emissions, etc is better with fuel injection, but hp (under WOT) is very close to the same.
I too, would have to see the dyno results to believe it.

 

To make sure the tests weren't skewed, I'd need to see an independent third party, without a vested interest in the results perform the dyno tests. Without that, it becomes just another form of marketing.

 

All I am suggesting is every performance claim be backed by more that seat of the pants dynos.. Time slips or dyno numbers with new multechs and new bosch 3 injectors same with milage and emissions do that and you have valid test results that can not be questioned anything less is an opinion by a customer that has no data either. I have yet to meet a car guy that did not rationalize an investment as an imporvement if no more than to feel better for the money spent. I have been an engineer for many more years than not so for me it is all in the numbers and no opinions.

 

If the Bosch 4 is better than the Bosch 3 then why wouldn't I want the Bosch4????? Not knowing what I am talking about I assume some how the 4 is incompatible with the C4.....and my LT4 in particular...??

How are the 4's better???

 

I would want all my competitors to keep buying those Multecs. Me, I will go with the new technology.

 

the problem with the bosch 4 for the ls2 is that they are too short to fit in the l98 you can't lower the rails.. There are Bosch 4 that are the right length but they are only available new and are about 75 each.. There are no cores around for rebuilts so it would not be worth the money IMO

 

Does anyone know anybody at a corvette magazine that would be interested in running a cool article about this. All they would need is a car with functional stock injectors, a new set of Bosch injectors, a little wrenching and a dyno day. It can all be done with an impartial view of the magazine. Any thoughts?

 

"Atomization" is the scientists $10 word for turning a liquid into vapor. It has been the basic part of fuel mixing from the first internal combustion engine. The Rochester carburator on the old SBC's "atomized" the fuel.

Not saying the Bosch 3's don't do it better than the Multecs. But I agree that when replacing old with new things seem to run better. Marketing is all about perception and the more $10 words the better. I would like to see a back to back dyno's in the same car with brand new injectors of both brands. My hypothesis is the HP difference if any will be 1HP or less.

But the Bosch injectors might be more consistant and reliable, which at the end of the day is what we really want from a fuel injector.

 

"My hypothesis is the HP difference if any will be 1HP or less."

Could be, but how much more fuel does it take to combine with the oxygen atoms to make the same power. With better atomization I would think it would take less fuel.

 

It's my understanding that injectors of different types can operate differently especially at partial opening/throttle -- that includes units with the same lb/hr rating. I'd wonder if the improvement (seen by the OP) was due to faulty operation of the OEM units vs atomization. Unless he's owned the car since new, the claim of running better-than-ever may indicate the injectors have been "bad" for a long, long time.

With our aging injectors, it's completely believable that having new injectors would help improve mileage/performance -- especially if the old units don't atomize very well. But, I also have to wonder if it can hurt. If there are part-throttle openings where one (injector) style delivers a significantly different amout of fuel it can't be "good". Is that something that causes immediate problems or could it take several thousand miles before negative results surface?

A simple swap and observation isn't very scientific. I would go so far as to think the option of buying a tune (from FIC) for stock TPI or LT1 might be a worthwhile service to provide on top of selling injectors. For stock cars, a generic tune should be as good as factory -- but better if geared to the specific operation of the Bosch 3's.

Though I loved Jon's video's, seeing a back-to-back real-world tests of new vs new injectors and their mpg/HP ratings would be very enjoyable. It would be much more compelling for the point of this thread.

 

What we are really talking about here, and someone correct me if I'm wrong, is not amount of fuel, but the refinement of the vapor. The "atomization" is a question of how fine is the vapor. As Greg alluded to one injector may perform differently at different performance demands. Say, at part throttle the Bosch sprays finer than Multec. A finer mist in theory creates a more even and complete combustion, thus releasing more energy. So the result would be greater low end performance and throttle response. Also the result would be hotter combustion temps and greater cylinder pressure for longer durations since we are talking low end (normal driving conditions). So, as was Greg's question, could this lead to premature head gasket failure, worn compression rings, failing spark plugs, valve train damage etc. etc.?

Then lets say, that because the Bosch injector as a result of the design that atomizes so well at part throttle, creates a "bottleneck" of fuel at WOT. So to in effect, restrict fuel. Would this then actually decrease performance? Could this also create a harmful environment by causing a lean condition? Whereas the Multec may not atomize as well at the low end and seem to not "perform" as well, but may actually perform better at WOT thus improving top end performance?

More importantly, the lesser "performance" of the Multec is actually designed to work with factory specs for things like valvetrain, head gaskets etc?

Yeah, you're right. probably not.

However it is fun to talk out of one's butt once in a while, so long as it is one's own butt.

P.S. the examples of "performance" above in no way actually represent the actual performance tendancies of either the Bosch or the Multec injectors. It was just a hypothetical "if this were so then that must be so" scenario. In the context of course that it came from the bottom of my chair

 

Discussion is a good thing. However is fuel collecting on the bottom of the runners by a poor spray pattern and running into the combustion chambers a good thing as the unburnt fuel could wash down the cylinder walls?

 

Hi,

I have dyno numbers from my LT1 with the stock injectors (within the past year). I just installed the Bosch III injectors. My actual problem was a bad fuel pressure regulator but also changed out the injectors (thinking that was my problem at first).

Well...I have to say (by TSOTP) it feels slower at part thottle-used to spin the tires in 1st gear. To be fair the last time I drove it was in the winter-with much better air conditions. Also I still have some old gas in it as I was not able to fully drain it all out.

I may put it back on the dyno and I will post my results!

Steve

 

Well why wouldn't better atomization which, being responsible in whole or part to a more complete burn, which in turn causes more psi in the combustion chamber...exert more force on the piston translating to more horsepower or torque?

 

Let me say that it might be quite posible that you would need to retune your car to see the full benefits from an injector swap. A tune for the Multecs may not be ideal for the Bosch 3 injectors with a better spray pattern. Just adding to the discussion.

 

When I swapped out the Multeks for Bosche III's I didn't notice a big power increase but I did get better mileage and faster starts. The biggest change occured when I installed an AFPR and bumped the pressure up about 8 psi. That gave me a solid boost in power.

The way it was explained to me is this: When the fuel is atomized better, the burn is more efficient. Since the burn is more complete, the O2 sensor sees a lean condition and increases the injector pulse. The result is more fuel in the chamber which equals more power. TPiS did dynos with an 85 stock 350 with an AFPR set to 47 psi. They got a 13 Hp increase. I happen to believe if Bosche III's had been available then, the increase would have been better. There would have been an even better spray pattern and atomization.

 

How do you use the Bosch III in a C4 without changing the fuel pump to handle the higher pressures? I have a set of LS1 injectors, but won't get the 28-29 lbs of fuel without increasing my fuel pressure, correct? Do I have to buy Ford injectors that run at a lower pressure to achieve the higher fuel rate of the Bosch III with the stock pump?

 

depending on which ls1 injectors you have either 26 which are 22 in a c4 or the 28 which are 24 in a c4.. .. if you put the same one in a Porsche that runs at even higher pressure then they are bigger yet.. The injectors output has a direct relationship with its input. What they are rated at does not mean they can't work at different pressures.

 

Are the short Bosch 4's Pico-sized?