Hi all!

I really have two questions in this thread, the car is a 89' IrocZ 350 TPI.

1) Can too high fuel pressure damage anything on my car? Can it cause a ticking sound from my (new/refurbished Bosch III's) fuel injectors?

2) Should fuel pressure be changed when replacing injectors?
When doing some refurbishment/tune-up this winter, I also replaced the fuel injectors to Bosch III's standard replacement 22 lb/hr. When tinkering I saw that the PRV (pressure regulating valve) on the fuel rail had an adjustable pre-load -is this per original or has it been added later?

The Engine runs "ok" but I'm not sure it runs all as it should and the injectors are ticking a bit. I've experimented a bit with the pre-load with no result to my pressure gauge (which obviously might be broken/misreading), it reads constantly at about 26 PSI when running even though it should have increased. I belive the fuel pump to be original.

Tips and ideas appreciated. Thanks!

Br,
Per

 

First, I'd imagine at some point, too high could damage something, but not so much the engine I don't think. More the injectors or fuel pump from over stress. That's not exactly expert advice, just my thinking. ...the screw on the adjustable fuel pressure regulator (AFPR) ...which is NOT stock, but LOTS of us use.... adds pressure as you screw it in. Maybe back it off a turn or two and start low next time you get out there and tinker. Oh, and the ticking is completely normal...some do....some don't. Don't worry at all.

Second, officially you don't need to change anything when you change injectors, unless your new bosch injectors are rated at a different PSI.....and.....I'm gonna bet lunch they are. My Bosch III's are rated at 39.15, and I'm guessing yours are too??? Stock is 43.5 PSI ....so to START.....I'd aim for 39.15 PSI on your gauge, BUT....you gotta remove and cap the vacuum line. With 26 PSI, I'm guessing you didn't. BUT.....that doesn't mean there's a problem, just that you didn't accurately get a reading. So long as you have a stock tune, with the stock rating of 22 pound injectors (which apparently you do) and they're set to whatever PSI the injectors call for....you should be good. Beyond that....I'd probably tinker with between 39 and 45 and see what the car likes. Do a search for TPI fuel pressure and there are discussions for days and days with everything from hardcore facts to tales of snake oil and magic as to the pros and cons of higher and lower pressures, extra fuel, custom tunes, etc. etc. It's all about what your car likes.

 

Many thanks Abubaca!

That's somewhat conforting to hear that the ticking can be normal and that you raise no alarm for running with a bit too high fuel pressure (if that is now the case). I guess that I shuold start with lowering the pressure first to see how the car reacts, of course lowering pressure when raising lb/hr (21 std. -> 22 repl.) also seems logical.

I guess I should try to get a correct pressure reading and don't trust my extra Accel gauge, which is worn and probably inaccurate. Thanks again for good info!

Br,
Per

 

Yes it does, but keep in mind it goes beyond the right amount of fuel. Higher pressure will also deliver a better spray pattern (so says the internet). Lots of modern fuel injected cars really like a specific pressure, beyond simply how much fuel is added or subtracted. .....so yes, tweaking pressure to fine tune is exactly what the AFPR is for, BUT....it's not as simply as running a lower pressure for different injectors. That may correct for fuel quantity, but the engine just might not like that pressure.

Now how MUCH pressure range do you have? ...and how MUCH extra or less fuel can you get away with....eeehhhhh......I'm not the one to say. You can search and read tons of info, but ultimately the car will tell you what it needs.

 

When I replaced my injectors with the 30lb Bosch IIIs from SouthBay Inj. on here, I read they are the same PSI as stock. This was 2008 I think. I wonder if the injectors have changed or SouthBays pressure rating of them has changed? Now I'm concerned lol. I don't even the see the 30lb ones listed on their site, I do recall I had to special order them though. Mine are set for stock PSI at idle using the proper procedure and I did all of my tuning using that setting.

Thanks Abubaca for posting that info! I'll have to look into this.

Alex

 

This is the actually sheet that came with mine. Keep in mind that I'm sure there are a gazillion different Bosch injectors. Probably. I mean I don't know for sure, but I don't see why there couldn't be several different Type III Bosch injectors for various make and models through the years. The point is more to know "what you have" though, so you can tune accordingly.

 

Our injectors are rated at GM pressure which is 43.5psi. You don't see them on our site because we will be launching a new website in the near future. We have plenty of products that are not listed on the existing site. If you need something that you do not see please contact us at any time as we more than likely have what you need.

 

Thanks for the verification, now I feel like I'm not loosing my mind lol.

Alex

 

LMAO....no problem

 

The one's I bought from you came with that sheet I attached, and show they were rated at 39.15 PSI. That sheet of course has been downloaded off the googles, but I checked the part number. Now I'm looking around to find the ACTUAL piece of paper I got....I know it's around here somewhere!

Found it. .....yes, it IS that exact sheet that I posted. Maybe I'm not understanding the rating properly???

 

Hey guys Frank here. Bosch 3's for the most part come through Ford Motor Sport. Ford doesn't make injectors, Bosch does. The data I put forth is from FMS and based on ford pressure, 39.15psi. So to use this table see the multiplier's. Yes they come from the internet, Robert Reports I believe. I have all oem Ford data up to 80lb, Bosch ad Deka . Hope this helps

 

Frank, I just wanted to clarify that what I've been saying is correct. I think it's real easy to get turned around with all the typing, and number, MATH, LOL!!! I Think I have it, but listening to what you said to 92GTA, I think someone (maybe me) got it turned around.

Just for example, let's take 92GTA's car. Assuming he's got the same 30 pound injectors that I bought, then we can agree that per that sheet I posted, they are 30 pound injectors, rated at a target of 39.15 PSI. ...and if when he tests his actual car, puts a gauge on the rail, he get's 43.5 PSI, as GM's TPI pressure regulator is designed to do.....then ultimately he's firing more fuel than the ECM thinks. It's behaving like a larger injector.

Now, forget about real world, the other sensors the ECM uses to correct for fueling, etc. etc. Just in theory......do I have that correct?

 

For the record Alex, my old engine had 24 pound injectors, and they were also rated at 39.15. I ran them, not knowing any better at all, at the stock pressure of 43.5 PSI. ...soooo not only were they slightly large, but they were getting higher pressure too. The car ran great, plugs never fouled, cat survived, mileage was good.....it wasn't until years later that I ultimately got it tuned, but I never had an issue. That's not to say someone else may have issues, but my point is that if your car is running well, I wouldn't worry.

 

It sounds like (please correct me if I'm misunderstanding) Frank is saying that Bosch makes these injectors to work in a range of psi for multiple applications, 39.15 if a Ford application, and up to 43.5 if a GM application. For example he says the data he put forward was based on a Ford application, hence the rating was stated as 39.15 when in actuality that's not the true rating, that's simply the psi they were being ran at for that application (Ford) when the data was measured.

Is that right Frank?

Abubaca, I do in fact custom tune my engine, have for 16 years now. When I went from my Accel 30lb to these Bosch 30lb, I went to go re-tune for them and found that I literally had to make zero changes anywhere for them. So I'd say that when they are ran at 43.5, they flow as if made to run at that psi (which they are, at the top of their operating range according to Frank). I know the Accel injectors were made for 43.5 only from what I recall and they seem perfectly comparable.

Alex

 

I agree that these injectors will work 100% fine in multiple applications, and both pressures listed are well withing their operating capability.
Again, I agree. Since they were made for Ford originally, I can assume Ford feels 39.15 was the ideal pressure, and at that pressure, they injected 30 pounds of fuel in one hour, so that's why the literature lists it as such.
This is where I disagree. An injector is an injector. There's not a true and untrue rating. Is just is what it is. It's an equation. Time @ given pressure = weight. 1 hour @ 39.15 PSI = 30 pounds of gas. If you run it for 2 hours, you're now going to have 60 pounds of gas in the bucket, but the injectors are no different, they're still the same 30 pound injectors, right?......and 1 hour @ 43.5 PSI = 32 pounds of gas. Still 30 pound injectors, but plug 'em in, and you're gonna pump too much gas.

....now we can argue that in the real world, this may or may NOT make any real difference. ...and if you tune your own car, it's irrelevant. BUT.....the OP asked whether or not he had to change anything to swap injectors, and if he replaced 22#@43.5 with 22#@39.15, then technically yes...he should tune for having 23 pound injectors, so the ECM drops out a little fuel. For the record, I would NOT bother doing that if I didn't have tuning equipment, but technically, you should.

Plug in the values in the calc below, and you'll see what I mean.
http://www.deatschwerks.com/resource...ure-calculator

 

Being that the data the sheet you posted from FMS does show 1.0000 at 39.15, I must agree with you. It looks like Bosch is making these to be designed for Ford applications and not GM applications. That or the data is pencil whipped.

I totally agree that the math is the math so that's the bottom line. Any so called "real world" argument would be BS too because each engine is in a different state of tune with 100s of variables. Apples for apples though, yeah the OP should drop the fuel pressure since these are apparently purpose made Ford injectors.

 

So does this mean if we replace with Bosch III's on a stock engine we should be getting it tuned ? Not infact plug and play as south bay advertises ?

 

Brett89, I think if you're using 22 pound injectors, and he says plug and play....they are probably just that. Plug and Play. I think you're good.

Now in general to anyone who stumbles across this, let me be very clear. ANY TIME....you don't put factory direct replacement parts on your car, you owe yourself the due diligence to research as many variables as possible, because short of fraud, you're the only one responsible.

Second, I bought my injectors from Frank a few months ago. He was awesome to deal with, and the injectors came with everything I needed (spec sheet) to determine what my injectors were, and what they were going to do. GM never put 24's or 30's in any TPI, and that's what SOOOOO many of us are using. If you post up backwoodshillbilly.com and ask if 22 pounds is the same as 24 pounds, then well.....I mean it's 2 pounds difference. I'm not sure how that could be plug and play. Again, see paragraph one.

Third, GM used 22# injectors in the 5.7 TPI. I went to the website, selected 22 pound Bosch type 3 for TPI 5.7, and it says:
Flow Rate: 22.3LB/Hour 232cc/mn at 43.5Psi
22 pounds is stock, and 43.5PSI is stock, so as advertised, yes, I'd suggest it's pretty much plug and play, as is advertised.

....but there are a LOT of injectors on that site. Several brands and several different ratings. I clicked on a few and the only that I saw that said plug and play were 22#@43.5.....which of course, would be stock replacement.

Southbay has a great rep on this site, he's a sponsor, and my dealing with Frank while short, were everything I needed and I was completely happy with the service, price, and product. I wouldn't hesitate to call him first for anything I needed that he offered.