rage2

[quote]Originally posted by Russ Murphy:
<strong>We had the same discussion about rage's car and maxing-out the stock injectors. His were maxed @ 8.5 psi and a number of folks were disbelieving of the FACT that he was a 100% duty cycle a that low of a boost level. After dynoing (well, sort of, the dyno couldn't provide enough resistance :eek
and on road dynoing the grossly increased efficiency was borne out. 404 ft/lbs I believe was the number. My injectors were operating a 100% approx. 12.5 psi and all of the fuel was combusting for sure since the motor started knocking at 13.9 psi with the injector duty cycle @ 109% with plenty of ign. retard (10 degrees).
If it quits raining I'll do a 60 to 100 4th gear pull. That should help clarify things. </strong><hr></blockquote>

When my car was first ran, it ran out of fuel at 8.5psi. Nobody would believe me, I even ran the car at 10psi and saw my A/F meter get to the greens on the LED (scary!)...

After popping in 72# injectors, I started getting knock at around 12psi on 91 octane. On 103 octane, I ran fine at 20psi. The dyno run hit 20psi at 4400rpm, which gave me 404ft-lbs TQ, and 339hp... boost dropped from there.

I then bought myself a Blitz Power Meter, which measures RWHP based on weight/acceleration from the wheel speed signal, so it's fairly accurate. On pump gas I dyno'd a 310rwhp (if I remember correctly) at 12psi, 91 octane, around 5900rpm. On 103 octane, 20psi, 380rwhp at 5700rpm (power from about 4200rpm-6000rpm never dropped below 330rwhp). The peak HP at 5700rpm was actually made at 18psi because I have a small vaccum leak right now that's causing boost to drop a bit up top.

Some more tuning with my new Wideband O2 should see me clear the 400rwhp mark. My injectors are at about 92% duty right now.

Outlaw952

The problem lies in that the stock turbo can only flow so much. This is directly related to the Volume of air, and the actual mass that you are pushing into the cylinders is determined by the density of that Volume. With a MAF, it will have more restriction, which means that higher pressures are required to max the flow of the turbo, which means the air is hotter, and therefore the density is less (air expands when hot), which means you are actually getting less air and are less efficient. With a freeflow intake like SDS, less restriction allows lower pressure required to max the flow of the turbo. The air is cooler, which means the density is higher, and you are actually getting more air mass into the cylinders. SO, more air is of course more power, but remember it is also cooler, and more dense, which means it has in effect reduced its volume per mass. When it ignites, it will heat up and expand to the combustion temp. Hot air charge has in effect already expanded some, so it will not expand as much when ignited(relative to volume per mass) and will not push on the piston as much as the colder air charge. This is why moving your cone intake away from the radiator helps (this will allow colder air charge).

Anyway, this is why at lower boost they can max out the injectors, they are providing more air mass thanks to less restriction on the intake.

Danno

"Completely understood, I just wouldn't have thought having a MAF on the intake side of the turbo would add that much heat to the intake charge."

Also adding a bit to Erick's and Outlaw's statements.

With restrictions in the intake before the turbo, there will actually be a vacuum before the turbo. So if you take the pressure delta across the turbo's compressor, to generate 12psi of boost, it may actually have to compress the air 20psi to make make up for the 8psi of vacuum on the intake side.

Then if you remove ALL intake restrictions before the turbo, it only have to compress the air 12psi to generate 12psi of boost. This will definitely heat up the air less than stock for the same boost-pressure at the intake-manifold.

Danno

whoops, deleted duplicate post...

rage2

Hey Danno, have you gone standalone on your car yet? I saw a post on SDS from last year saying you were about to go with SDS =).

Curious what you ended up going with.

Rob

First off. this has been a great thread.

Second, Rage2 (and Russ), It's not that I don't believe what you guys have been posting (I do), It just that I'm shocked by it and don't fully understand it.

[quote] Then if you remove ALL intake restrictions before the turbo, it only have to compress the air 12psi to generate 12psi of boost. This will definitely heat up the air less than stock for the same boost-pressure at the intake-manifold. <hr></blockquote>

Good point, but I would have still thought that the air filter was the largest restriction on the inlet side of the turbo. I am just shocked that basically a MAF would be that much of a restriction to the intake.

Another point of interest to me is the 109% duty cycle. Could it be possible that the SDS displays a reading of 100% injector duty cycle when the actual duty cycle is 80% (since 80% is the maximum duty cycle recommended by most injector manufacturers and also since most injectors stay open constantly at about 93% duty cycle) This would make some sense of the &gt;100% duty cycles since a 109% displayed would be then equivalent to 87.2% actual. Any thoughts on this?

Finally, Russ, When you get to where you happy with the fuel & ignition settings for the stock injectors, would you e-mail me a copy? I think I feel a project coming on.

Later,
Rob

Danno

"Hey Danno, have you gone standalone on your car yet? I saw a post on SDS from last year saying you were about to go with SDS =)."

Yeah, I sent them a cashiers-check for the EM-3 4F system over a month ago and... nothin'! I got a call from my tuner-shop today saying that Ross needs to talk to me about the mods on my car... huh? I ordered the package with a 3-bar MAP and I figured that's the only variable that would need to be considered from their end. Anyway, I'll call Ross Tuesday morning to see what's up...

Russ Murphy

Rob,
No problem, I'll happily email them and I'm slowly getting there. I guess that rage's big turbo and the headwork has made it so that his fuel map is quite different than mine. About the duty cycle, I believe that when I see duty cycles above 100 they represent what the fuel values are "telling" the injector to do and if it shows 112% on the screen it means that the ijectors are 12% short of delivering the fuel goal. I've emailed SDS to check about this.

tecart

russ greaty job, keep up the tuning work please, id like to find out when the car is all done, how fast the car is, and its total rear wheel horsepower, also my k26 smoked the wheels more in 1st and 2nd than it did later on as i switched to a k29 with a maf#4 kit, so i think that above 5000 rpm you will start to lose power fast but that isnt saying your car wont hit 330 rear wheel horses, but let us know how the boost gage falls as you approach 18 psi at full boost, will it fall off to 14 or stay at 18 or something else, that id like to know, also that will tell you if you want to upgrade to a bigger turbo or not, my k29 holds 22 psi to redline on stock injectors with my adj. fuel reg. set to 60 psi w/ vac. hose disconnected and im running out fuel for more power too, i also wonder what you total investment is at this point 1500? or less or more? and i would be interested in the bracket too someday as i think im going this route also, thanks for keeping this thread updated and let use know about any full boost runs ok, also to danno if you read this i had k29 chips that flowed too much fuel for my k29 without the maf#4 kit at low end but fine at high end, but now i got the maf#4 kit i need that fuel but im running k27 chips, no i got good fuel low and too little up high, my question is how can the dme k29 chip flow so much more fuel verses the k27 chip, i mean i got the fuel to 60 psi, and a high flow fuel pump too and i still cant get back to the k29 chip fueling? i even got the arc2 on mid and high turned to 4:00, i can only get to the 1st green light at full boost on the arm1 display, i know i need bigger injectors for saftey and power here but can the k29 chip flow the fuel like i had 52 pound injectors instead of the stock 37 pounders? or is that not possible, basically what im trying to say is that the k29 chip i had last year in the car without the maf kit at that time flowed as much fuel or more than i get now with the k27 chip and arc2 set to 4:00 on mid and high and a bigger fuel pump all though the stock 37 pounders, what gives? again i know i need bigger ones but is there a special thingy about the k29 powerhaus autothority dme chip? i know its meant for 3.0 liter motors or 2.8 with monster turbos david raines told me when we tried it out when i got my k29 from them last year... thanks for reading <img src="confused.gif" border="0">

Tom Pultz

[quote]Originally posted by tecart:
<strong>thanks for reading</strong><hr></blockquote>You'd better thank us... are you going for the world's longest paragraph without punctuation?

tecart

i do that often and i always get someone mad so your right but i would like danno to respond if he reads the bad english

rage2

60psi fuel pressure (4 bar)... is it safe to run that high?

tecart

rage the 59-60 psi im running now is only a sort of test period, like im not gonna leave it here for any long time period. But the 60 psi is needed to keep my car from going below blue on the arm1, so i have to for now, 54 psi fuel didnt get me into the blue at even 4:00 on the high **** of the arc2, also i was told it wont damage anything, but it could actually lower the fuel reaching the injectors will too much fuel pressure although i havent had that happen and was advised that my 60 psi is the limit for fuel pressure and any thing more would do nothing for my small injectors except possibly ruin them

aka 951

4 bar total fuel pressure should be no problem. I used to run 4 bar at idle on my 86 951 (for a total of about 5 bar on boost). The cup cars along with guys with tweaked 996TTs run similar fuel pressures.

pikey7

Guys,

This has been an extremely informative post. Thanks for all of the input given by you experts out there.

Just one piece is missing. What do you actually need to have to successfully install a standalone management system?

Obviously you need the basic system (which I assume is all the computers, sensors, and the 'coil' replacement), and as I can read, you need to fabricate a crank pickup bracket. But is that it??

I can feel $1300 disapearring rapidly from my pocket...... Anyone interested in a LR MAF and Kokeln chips?????