Notices
928 Forum
Sponsored by:
Sponsored by: 928 Specialists

Roll on to 140mph with a Twinscrew"Supermodel"

 
Old 02-09-2005, 02:40 PM
  #16  
Tony
No wide loads, please!
Lifetime Rennlist
Member
Thread Starter
 
Tony's Avatar
 
Join Date: May 2001
Location: Las Vegas
Posts: 13,130
Likes: 0
Received 0 Likes on 0 Posts
Default

What do i make of the data and the questions?
In no particular order...

1)Well...i know my logworks and LM1 appear to be working and logging well.

2)My boost isnt dropping of at redline like it did on the dyno. This could be a characteristic of a dyno pull vs a street pull? When i replaced my 30#injectors with 24# i sealed up the manifold as tight as a drum...there is no way air is leaking from it now as far as i know! The car idles much better and the idle stabilzer maintains the rpm with out hunting up and down now.
I also didnt look at my A pillar gauges as i was too busy looking at the road and for a flash of RED light from my AFR meter telling me to shut down. I didnt get a look at my fuel pressure either. As good and as close as that pod is to my eyes i was still too concerned about the road in front of me ....as one should be. The road was actaully up hill a bit and with a sweepign turn to the right. (For the locals, left turn on to the Beltway from Towncenter..exited at Sahara)

3) i could be a bit leaner.

4)The I/C seems to work pretty good.

5) the air at the mouth of the inlet to the SC is still 20-30F+ warmer than at the filter in the fender. Time to inuslate the inlet system from the fender to the SC or go back to the way Andy has the inlet running along the valve covers. I dont think im loosing much power due to this temp gain to warrant changing the way it looks. I like the clean look of the engine with out the air inlet along the top of the cam covers. Each his own of course. The test will be this summer as i think the fender will get much hottter in the sun as will the aircharge there and it will be more detrimental than one in front of the radiator, where my"PLAN B" is putting it.

6) The pulley is 2 5/8"..as measured from the outside edge to edge across the center. Is it measured there or at the bottom of the groves? Its the smaller of the two that you sent originally Andy.

7) I stopped at 140 as that seemed a good place to stop with the flashing lights of a tow truck down the road on the shoulder as well as traffic closing rapidly. This car has 180+ in it IMHO.

8) yup, that is the time along the bottom.

9) as far as the dicharge temps, thats what it shows, thats all i know. Although under boost, i think the SC is barely working with the current pulley ratio. I wish i would have had my TC(thermocouple) set for MAX temp on the discharge temp. The TC's are right next to the GM temp sensors i have for the AUX BOX. Perhaps i have them calibrated wrong? I will have to do a similar run but keep an eye on the TC's reading instead, they are DEAD ACCURATE. I calibrated the Logworks temps scale against the temp reading on the TC's. Example: the TC display said 60"F and the GM sensore said 64. I slewed the voltage a fraction so the AUX box/GM sensor matched the temp. shown on the TC. I also do this for boost as Atmospheric pressure changes from day to day...i zero it out on the guage with the engine off. It only changes it .1-.4 of a psi and i only do it when im doing "a run"
I like to think i have the LM-1 pretty well dialed in but may be that slight adjustment to the temp threw the rest of the temp scale off? However, it was only 4 degress off anyway. Somewhat hard to explain unless you have used the program. Blown Beast and Z will probably follow that.

10) I can only say that those are the times displayed on the logworks program. It seemed long to me as well, but like i mentioned it was up hill and thats what it displayed... thats all i can say.
10 sec to 100 mph is pretty quick i beleive?.

From a website:
2005 911 Turbo S Specification (Coupe)
0-62mph: 4.2 secs
0-100mph: 9.0secs


Consider trap speeds and 1/4 mile times. My car stock/NA did 14.4-7sec and 97 mph in the 1/4 mile. Ill find out in 2 weeks exactly what it will do now

In all, this was the first time i have done this and logged any data, so Im sure there may be errors and i will discover more as time and the miles go by. I just wanted to share what was going on during a highspeed typ run. Actually you guys probably have more answers than i do

Tony is offline  
Old 02-09-2005, 04:52 PM
  #17  
mspiegle
User
 
mspiegle's Avatar
 
Join Date: Nov 2003
Location: Redondo Beach, CA
Posts: 1,574
Likes: 0
Received 0 Likes on 0 Posts
Default

That's pretty sweet. I'm lovin' your logging graphs. Do you think you'll be able to videotape your 1/4 mile runs? I can host anything, so try to videotape and make a really high-quality video.
mspiegle is offline  
Old 02-09-2005, 08:37 PM
  #18  
Lagavulin
User
 
Lagavulin's Avatar
 
Join Date: Mar 2003
Location: New Berlin
Posts: 1,286
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by Tony
Duty cycle runs up to 100% (it did with the 30#injectors also BTW)
A/F looks good, not near as rich as it was with the 30# but I still have some tweeking to do.
Nice write-up Tony!

<--- That's Tony working on his AuxBox...

No matter which size injectors you have in there, the duty cycle will max out at the same exact point if you are running the stock MAF and fuel computer. The computer was programmed from the factory with the car running 19 lb'ers NA.

Essentially what's happening is that after a certain CFM and corresponding voltage input from the MAF, the computer goes 'brain dead', and responds by telling the injectors to stay open all the time; it doesn't care what size they are since it assumes 19lb injectors. Remember, at WOT, the computer is open-loop and ignores the O2 sensor input which means the only information available is from the static fuel maps using MAF voltage and RPM as inputs which were made with 19lb injectors in mind. The way we currenlty 'overcome' that limitation is by continually raising the fuel pressure based upon boost so more fuel can be pushed through the locked-open injectors to keep up with the additional air being crammed down it's throat. No doubt, definitely Fred-Flintstone, but it does work, and works well enough on low-boost applications.

So, that is the biggest hurdle for our supercharged cars right now is a good tune without resorting to 'Super FMUs', etc. And that means using properly sized injectors with the ability the modify the fuel maps accordingly for a nice idle and cruise while running 12:1 at WOT, none of which is currently an easy thing to do with our old-*** cars.
Lagavulin is offline  
Old 02-10-2005, 08:41 AM
  #19  
John Speake
Addict
Rennlist Member
 
John Speake's Avatar
 
Join Date: Feb 2002
Location: Cambridge England
Posts: 6,901
Likes: 0
Received 4 Likes on 4 Posts
Default

Hi Lag,
We're working on it !
John Speake is offline  
Old 02-10-2005, 03:12 PM
  #20  
blau928
Addict
Rennlist Member

 
blau928's Avatar
 
Join Date: Feb 2004
Location: Monterey Peninsula, CA
Posts: 2,304
Likes: 0
Received 0 Likes on 0 Posts
Default

Go John,

I have not forgotten our discussions...!
blau928 is offline  
Old 02-10-2005, 04:47 PM
  #21  
B951S
User
 
B951S's Avatar
 
Join Date: Jul 2003
Location: on the edge
Posts: 802
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by Lagavulin
Nice write-up Tony!

<--- That's Tony working on his AuxBox...

No matter which size injectors you have in there, the duty cycle will max out at the same exact point if you are running the stock MAF and fuel computer. The computer was programmed from the factory with the car running 19 lb'ers NA.

Essentially what's happening is that after a certain CFM and corresponding voltage input from the MAF, the computer goes 'brain dead', and responds by telling the injectors to stay open all the time; it doesn't care what size they are since it assumes 19lb injectors. Remember, at WOT, the computer is open-loop and ignores the O2 sensor input which means the only information available is from the static fuel maps using MAF voltage and RPM as inputs which were made with 19lb injectors in mind. The way we currenlty 'overcome' that limitation is by continually raising the fuel pressure based upon boost so more fuel can be pushed through the locked-open injectors to keep up with the additional air being crammed down it's throat. No doubt, definitely Fred-Flintstone, but it does work, and works well enough on low-boost applications.

So, that is the biggest hurdle for our supercharged cars right now is a good tune without resorting to 'Super FMUs', etc. And that means using properly sized injectors with the ability the modify the fuel maps accordingly for a nice idle and cruise while running 12:1 at WOT, none of which is currently an easy thing to do with our old-*** cars.
Great info, that was actually goning to be my next posted question, something along the lines of "blown motor fuel control without electonics?".

Would it be possible to use a MAF signal massager to re-scale the MAF signal so full load with a blower gives 5v and idle still gives stock like voltages. You could then ditch the the FMU and dial in bigger injectors...a la Split second/huntley , or even better Powerperfect piggback, LR MAFterburner etc.

I am suprised none of you blown guys do this, I am also equally suprised at how good a result you are getting by not doing it!

I don't think I would be too happy with 100% DC on the injectors for too long though.
B951S is offline  
Old 02-10-2005, 04:58 PM
  #22  
Bill Ball
Under the Lift
Lifetime Rennlist
Member
 
Bill Ball's Avatar
 
Join Date: Mar 2002
Location: Buckeye, AZ
Posts: 18,482
Likes: 0
Received 0 Likes on 0 Posts
Default

Yes, this is a very interesting discussion. I can only listen and try to absorb, and I'm anxious to see if this results in some new fuel management ideas and products.
Bill Ball is offline  
Old 02-10-2005, 05:17 PM
  #23  
John Speake
Addict
Rennlist Member
 
John Speake's Avatar
 
Join Date: Feb 2002
Location: Cambridge England
Posts: 6,901
Likes: 0
Received 4 Likes on 4 Posts
Default

QUOTE""Would it be possible to use a MAF signal massager to re-scale the MAF signal so full load with a blower gives 5v and idle still gives stock like voltages. You could then ditch the the FMU and dial in bigger injectors...a la Split second/huntley , or even better Powerperfect piggback, LR MAFterburner etc.

I am suprised none of you blown guys do this, I am also equally suprised at how good a result you are getting by not doing it! END QUOTE

It's not as easy as it sounds, there are hardware and software limitations which means this is very difficult to achieve. That is not to say that I am not still working on these problems...

We do have an 8psi car running with 30lb injectors, no FMU, stock fuel system - just remapped. We hope to soon have a solution for higher boosts and 42lb. Soon being a relative word...
John Speake is offline  
Old 02-10-2005, 05:23 PM
  #24  
GoRideSno
Super User
 
GoRideSno's Avatar
 
Join Date: Feb 2002
Location: Redondo Beach, CA>>>>Atlanta,GA
Posts: 2,015
Likes: 0
Received 0 Likes on 0 Posts
Default

Hey guys,
I have never seen a fuel curve during a steady pull from one of my setups that varried by more than about 1 AFR point from start to finish.
That's probably as good as stock.

With my systems untill you have reached the usefull hp limit for 30# injectors there is no need for any change or additional Mgt. As a matter of fact I am even thinkng I will be able to do away with the 2025 piggy back regulator and use only 928 parts and larger injectors.

John Speak is comming out with an interesting item that will benefit all 928s. I'll be getting one of his units for myself just for fun.

HTH,
Andy
GoRideSno is offline  
Old 02-10-2005, 08:06 PM
  #25  
B951S
User
 
B951S's Avatar
 
Join Date: Jul 2003
Location: on the edge
Posts: 802
Likes: 0
Received 0 Likes on 0 Posts
Default

Its running the injectors at 100% that would make me a little concerned. Like I said, I am amazed that you guys do such a good job with just pressure regulation. The 944 / 911 turbo guys usually have to go electonic (stand alone like me or MAF signal massengers etc)

Way to go....guys!
B951S is offline  
Old 02-10-2005, 10:16 PM
  #26  
Tony
No wide loads, please!
Lifetime Rennlist
Member
Thread Starter
 
Tony's Avatar
 
Join Date: May 2001
Location: Las Vegas
Posts: 13,130
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by John Speake

We do have an 8psi car running with 30lb injectors, no FMU, stock fuel system - just remapped. We hope to soon have a solution for higher boosts and 42lb. Soon being a relative word...
Very cool.

Its running the injectors at 100% that would make me a little concerned.
I believe even in NA stock form the 19lb injectors see 100% duty??

Tony is offline  
Old 02-10-2005, 10:42 PM
  #27  
klatinn
User
 
Join Date: Oct 2004
Posts: 29
Likes: 0
Received 0 Likes on 0 Posts
Default

Hi Tony,

If you read your chart right there's more info there:

1. Your AFR curve goes up linearly with RPM because your injectors are maxed out. With rising RPM more air flows into the engine but with max'd injectors the fuel flow is constant. Result is progressively leaner operation. You are hitting AFRs in the 12's, which is fine, but you could actually use bigger injectors, provided you can somehow keep the ECU from maxing them out anyway (piggyback ECUs work good for that, or MAF eliminators like the Ford Mustang guys are running).
Injectors should not be run at more than about 80% duty cycle as a rule.

2. Your boost rises slightly when you shift (RPM jump to lower) and falls with increasing RPM. This could be pressure loss in the intake path (air friction in the pipes/IC).

3. Your AFR is fairly rich (in the 10's) when the injectors are not maxed out. In that area you are loosing power because of the richness.

4. Your setup for the GM IAT sensors might be wrong. Did you just put in 2 points in LogWorks, like just 2 voltages/values? IAT sensors are non-linear and need a linearisation table. If you search on the internet (for example in diy-efi.org) you'll find the resistance curve for the GM sensors. On the innovate web-site is a little spread-sheet from which you can create a linarisation table for LogWorks if you also put in the load resistor value.

5. The IAT and discharche temps follow the boost relatively slowly. This is due to the thermal mass of the GM sensors.

As to increasing fuel pressure with boost (rising rate regulators): there's a limit to how much you can do. The fuel flow increases with the square-root of fuel pressure difference between manifold and FP.
Double the pressure difference increases the flow only by 41%, but the fuel pump flow capacity goes down dramatically with increased pressure.



Regards,
Klaus
klatinn is offline  
Old 02-11-2005, 12:15 AM
  #28  
Jim_H
Banned
 
Jim_H's Avatar
 
Join Date: May 2001
Location: The Great Northwest
Posts: 12,264
Likes: 0
Received 1 Like on 1 Post
Default

Klaus, Good stuff! Thanks!
Jim_H is offline  
Old 02-11-2005, 03:21 AM
  #29  
BrianG
Addict
Rennlist Member

 
BrianG's Avatar
 
Join Date: Jul 2002
Location: Edmonton, Ab
Posts: 2,286
Likes: 0
Received 0 Likes on 0 Posts
Default

Tony, I plan to hook up my LM-1 and Aux-box to get some of this info, ahead of disassembling the stock configuration. Of course I won't have the temps that you have at that point.

I hope you'll lend me a hand in figuring out how to set the thing up for some of those "other: sources!
BrianG is offline  
Old 02-11-2005, 11:43 AM
  #30  
B951S
User
 
B951S's Avatar
 
Join Date: Jul 2003
Location: on the edge
Posts: 802
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by klatinn

4. Your setup for the GM IAT sensors might be wrong. Did you just put in 2 points in LogWorks, like just 2 voltages/values? IAT sensors are non-linear and need a linearisation table. If you search on the internet (for example in diy-efi.org) you'll find the resistance curve for the GM sensors. On the innovate web-site is a little spread-sheet from which you can create a linarisation table for LogWorks if you also put in the load resistor value.
Try this...
Attached Images  
B951S is offline  

Thread Tools
Search this Thread

Contact Us - About Us - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: