txhedg

here is a copy of the injector service output report...if the pic doesn't work click the link to see it on my web site.



<a href="http://members.rennlist.com/txhedg/951%20Injector%20Calibration.pdf" target="_blank">Injector Service Report</a>

aka 951

Hmmm - I think something is wrong here. According to your injector cleaning results, your injectors are rated at about 370 cc/min at about 2.9 bar which equals about 35 lb/hr (divide by 10.5). In the above post you stated that they were at 42.9 I believe. I was hoping the first figure was correct, but if not please inform. I know of a guy that made 379 hp to the wheels on the stock injectors - thats why I'm starting to get concerned about all the discrepencies. Is it possible that 944 injectors were different flow rates for different years?

Danno

Interesting... I think there's something screwy going on with the injector flow-rates from either Bosch or Porsche here. For example, take a look at at Tony Garcia's test on the same injectors:

<a href="http://www.tonygarcia.org/injectors/stock25bar80percent.jpg" target="_blank">http://www.tonygarcia.org/injectors/stock25bar80percent.jpg</a>

His average flow-rate of 262.8cc/min@36.25psi is completely different from txhedg's rate of 372.0cc/min@43psi. Even if you bump up Tony's injectors to 43psi, the flow-rate would be:

• SQRT(43psi/36.25psi)=1.089
• 1.089 x 262.8cc/min = 286cc/min
• 286cc/min / 10.5 = 27.3lb/min

So it looks like Tony's injectors would flow 30% less (372cc/286cc) fuel than txhedg's for the same 43psi fuel-pressure. Bizarre...
Now I would tend to believe txhedg's injector-report more because, one, it's a newer run, and two, the HP ratings at the bottom would match the stock power-ratings more closely. At a BSFC of .55, those injectors should be good for 206.1bhp @ 80% duty-cyle.

This is below the stock 951's rating of 217bhp. But what about the TurboS's 247bhp? Don't tell me Porsche's overdriving the injectors as it comes out of the factory? And what about all the other hot-rodded 951s that have 300rwhp? That's 350bhp! Or how about Erick's 379rwhp sample? That's a whopping 446bhp, about double the stock power levels. How can one fuel-injector do this? I suspect there's different flow-rates coming out of the Bosch factory with the same part# here...

You may notice on the report that the same injectors Bosch# 0-280-150-803 were used in both tests... Quite odd...

txhedg

Being engineering math-challenged, I didn't know how to do the cc to lbs calc. Instead I used the Total System 141.71 lbs/hr figure, divided by 4, and came up with about 43 lbs/hr per injector....maybe this was wrong......where's an engineer when I need one????

whats the right way to do it?

aka 951

The 370 rwhp car (at 17 psi on pump gas) that I have the info on is either an 88 or 89 Turbo S. Basically the tuner cranked the FPR up (how high I don't know). In a nutshell, the head was slightly worked, it had a K29, autothority mass air, ceramic coated pipes and some other minor items (including extra oil cooler). If anyone wants a copy of the specs for the motor email me off list and let me know as I have the info on my computer at home.

Danno

[quote]Instead I used the Total System 141.71 lbs/hr figure, divided by 4, and came up with about 43 lbs/hr per injector....<hr></blockquote>
141.71 / 4 = 35.4275 ???

aka 951

Houston...we have a problem...how do 951s with stock injectors achieve such absurdly impossible hp numbers?

Danno

I think the math model is just a general guideline.

But that still doesn't explain the vast differences in fuel-flow for the same injectors with same part# used in Tony's and Tom's cars. Wierd.

Konstatin even mention on the email digest that the 968 Turbo RS uses the same injectors as well and that's a 345bhp car!

I wonder if we'll ever get to the bottom of this..

txhedg

danno -

oops , I slipped a number on the calculator....I had run 171.4 div by 4 = 42.9 (incorrect), it is indeed 141.7 div by 4 = 35.4. Its that damn dyslexia acting up again <img src="graemlins/c.gif" border="0" alt="[ouch]" />

txhedg....I love my 915

Danno

Yeah, I understand... I occasionally have lexdysia problems too.

Peckster

I just got my stock injectors cleaned by a shop that specializes in this, and they told me they were running at 92 to 93 cc/min before and over 95 after. They said they were tested at 45 (lbs./in?) Whyis this so different from what you guys are getting? I asked and he said it was probably a different machine, but that doesn't sound right to me.
Any ideas?

Konstantin

the rate is 372cc/30 se!
they got only 93cc/min????

i think they have no idea what they messured. They probably used the wrong conversion number.

Konstantin

Peckster

Wierd, you'd think these guys would know what they're doing...it's all they do!

Anyhow, I just put them back in it and runs about the same as before, still uneven, surging acceleration under partial throttle, but strong. I saw on an old post where one guy thought it was a weak hose running to the intercooler pipe, I think. Has anyone else had that problem. My hose is flexible, but seems to be in good condition. However, it runs over a steel line that puts a bit of indent in it.

Glad I got my road test in this afternoon. This morning it was raining hard enought to wash the salt off the roads, but now it's snowing again.

jp

Danno

John, the guys that tested our injectors didn't do a static-flow test (open 100% of the time). On your test sheet, there should be either a duty-cycle number or a pulse-width number in milliseconds.

Peckster

Test sheet? Don't forget, I was paying in Canadian dollars. You don't get no stinking test sheet for C$25.

I realized after going back that these guys deal mainly with diesel injectors. Still, mine look nice and shiny now.

And it was a hell of a lot cheaper than buying new, which my mechanic (no names here) recommended.
jp