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Matt47DGO
Dodge Dakota
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2/12/2003
16:27:27
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 Subject: 4.7 help
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I brought my truck in for a SC installation to a reputable mechanic that has built alot motors(Kenne Bell Distributor), anyway to make a long story short the job grew into the following: 2001 4.7, Kenn Bell SC w/optimizer, forged pistons 8.1 compression, Hi output heads(mild port/polish), Hi output cam, 24LB injectors. Apexi air fuel regulator, 3.92 LSD
When the truck goes on the dyno, it makes great power up to 4800 RPM then it lays flat all the way to 5400. Total 248 RWHP.
He says he's checked everthing; boost is good, air/fuel @ 12.5, not loosing timing. This thing should be making at least 300 RWHP. It runs great, just isn't making any power.
It's not good when the guy working on your car says he's stumped!
Any help would be greatly appreciated.
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Demon Dakota
DakotaEnthusiast
 
2/12/2003
18:27:25
|  RE: 4.7 help
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What's your overall compression ratio? Those pistons look to be way too low CR. The stock 9.3:1 ratio would be more ideal (unless you're really going to go super high boost, but you don't appear to have enough work done for that). It could be the KB Optimizer II as well. Something is definitely fishy with that install or S/C unit to only be making 248 RWHP. That's like only 3-4 PSi (maybe). Clogged cat? What kind of exhaust setup do you have? This is definitely not right...
K&N Drop in AF
True Dual exhaust and removed third cat
HO Cams & HO Intake
Modified TB
Autolite 3923 Plugs
TPS @ .76 VDC
IAT Adjuster Mod
14.52@94.2 MPH at Silver Dollar Raceway
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Matts47dgo
Dodge Dakota
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2/12/2003
18:41:27
| RE: 4.7 help
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Compression ratio is 8.5:1. Tried 10-11&12 lbs boost-No change. The boost pressure is there. Tried running straight pipes, made 3 HP difference. Sent the optimizer back 2x for different flashes, no change. It seems somthing is governing the motor, it runs good but no power.
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BeeKota
Dodge Dakota
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2/12/2003
19:56:46
| RE: 4.7 help
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It's the PCM it's not mapped past 5400 thats why it falls flat,Make you want to run out and get another 4.7!!!!!!
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kevster
Dodge Dakota
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2/12/2003
21:12:47
| RE: 4.7 help
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I dont know much about this stuff, but if you have a Jet module or something else in line with the stock PCM it will not work with the set up you have now. What does Kenne bell say??
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kevster
Dodge Dakota
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2/12/2003
21:14:25
|  RE: 4.7 help
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Hey what about your timing, is it right on?? do you have enough fuel being delivered to the motor? Fuel preassure? is it ok?
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HSKR
Dodge Dakota
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2/13/2003
00:06:13
| RE: 4.7 help
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Where is the knock detector for the KB optimizer located at and it it retarding your timing??
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HSKR
Dodge Dakota
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2/13/2003
00:09:10
| RE: 4.7 help
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Just to add on to what I posted already. The KB kit for the 5.9 won't run good after 4800 either. It's the KB optimizer that is the problem. For some reason it starts retarding the timing at that point because it "senses" detonation.
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notchlx
Dodge Dakota
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2/13/2003
02:24:42
| RE: 4.7 help
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Dude,
I definitely believe it has a lot to do with your compression ratio. As you stated, the A/F is at 12.5, which is a safe but pretty optimal setting (so it's doubtful there's a problem with the fuel). Do you have a copy of the dyno? It's too hard to believe the 10psi, is only good enough for 248RWHP. Somebody that knows the specifics of compression can enlighten you more, it's too late tonight to get into all of that.
I'm running the 6psi Paxton Novi-1000 kit, on a bone stock 2000 4.7L. With no tuning what-so-ever, it laid down 304RWHP and 351RWTQ.
What was the total timing on the dyno runs? I believe full cycle, mine was 21, and my A/F averaged 13.5
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Demon Dakota
DakotaEnthusiast
2/13/2003
11:16:52
| RE: 4.7 help
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That's what I'm saying notchlx! If the KB Optimizer is retarding timing based on what it sees as detonation (the KB Opt II might be in error), coupled with the fact that the overall CR is so low, leads me to believe that sucker is not set up properly to begin with. Stock compression is 9.3:1. That's plenty low enough to have 8 PSi on the KB kit with no preignition problems, and no timing pulled (if you run good gas). Run a stand alone FMU with your trucks current CR and I bet you can get 350+ RWHP with tuning at your boost levels. It's got to be in the CR (and maybe combined with the KB Opt II).
K&N Drop in AF
True Dual exhaust and removed third cat
HO Cams & HO Intake
Modified TB
Autolite 3923 Plugs
TPS @ .76 VDC
IAT Adjuster Mod
14.52@94.2 MPH at Silver Dollar Raceway
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notchlx
Dodge Dakota
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2/13/2003
12:00:46
| RE: 4.7 help
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Good! Glad we're in agreement.
Now where does he go from here?
Put the stock pistons back in, or get the higher compression ratio ones in there. Or...Try to tune the thing?
I'm sure the mechanic will love that, so will your wallet.
Run 9.5:1 at 8psi, and your 24lb injectors along with the auxillary injectors...Of course you would have to have them flash the Optimizer again.
Damn, that Sucks! Experimenting can sometimes lead to loss of sanity.
Just trouble shooting with you, maybe someone can come up with a easy solution.
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Matts47dgo
Dodge Dakota
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2/13/2003
13:31:47
| RE: 4.7 help
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Thanks for the replies,
We lowered the compression to run more boost(10-12psi). I know there is a drop in HP when you lower compression but the gain running more boost should be worth it. We already melted the stock pistons, went with custom Ross Pistons/Crower rods, don't even want to think about going back to stock. I agree the timing would do this but it was checked on the dyno with and without the optimizer with no change, we also tried two different PCMs.
Demon: the one thing we didn't do is install a stand alone FMU. the A/F stays steady at 12:1 do you think it's not getting enough fuel?
Notchlx: your right, wallet-sanity all out the window.
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Demon Dakota
DakotaEnthusiast
2/13/2003
13:35:06
| RE: 4.7 help
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I am positive a stand alone FMU would help, but is there a system for the 4.7L setup? I haven't really looked into that... There is a FAST system, but it's quite expensive I hear.
K&N Drop in AF
True Dual exhaust and removed third cat
HO Cams & HO Intake
Modified TB
Autolite 3923 Plugs
TPS @ .76 VDC
IAT Adjuster Mod
14.52@94.2 MPH at Silver Dollar Raceway
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Matts47dgo
Dodge Dakota
JOIN HERE
2/13/2003
13:49:31
| RE: 4.7 help
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I think Duner has a Vortech FMU setup. wouldn't be suprised if he modified it.
Duner, you out there!
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Duner
Dodge Dakota
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2/13/2003
17:51:06
| Just some ideas........
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Here I am!
I would check few different things.
Is the air filter flowing enough air to keep up with the blower? Try it without the air cleaner installed.
Is the catalytic convertor causing a backup in the exhaust system? With the stock cat - even a little extra richness on the A/F will cause it to become a problem
Is the belt slipping on the blower? Are you making full boost all the time? or does it fluctuate?
Is the spark plug gap too wide causing the ignition to not be able to fire at the higher rpms under boost? I ran into this problem with my alcohol injection and extra fuel. I'd make sure the plug gap is .032" to .035".
Is it possible that one of the newly installed cams is off a tooth?
What kind of fuel pressure is getting to the fuel rails when under boost?
What kind of voltage reading from the TPS?
Are you getting full throttle? (simpler things have been overlooked before)
Those are just a few things to check to try and troubleshoot the problem (your mechanic has probably already covered most of them).
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conig
Dodge Dakota
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2/13/2003
18:08:13
| RE: 4.7 help
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an apexi afc has such a wide range it should be easy to tune the fuel right, I don't think stand alone fuel management would be neccasary.
is there a popoff or blowoff valve for the kennebell? is it possible you have a boost leak. intake gasket any were psi can leak out?
thats all I can come up with. or maybe the cams are looseing effiecentcy(spelling) in the higher rpms.
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Heavyweight
Dodge Dakota
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2/13/2003
18:39:26
| RE: 4.7 help
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Sealing probs do occur with Kenne Bells. Duner has some great checks. Spark is a major issue, since of the low compression, it is even more important. A bad Cat will deffinately be a cork, I have seen this on Mustangs.
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Matts47dgo
Dodge Dakota
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2/14/2003
13:57:27
| RE: 4.7 help
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Thanks for all the input guys,
Went over everything with the mechanic, says he's checked everything-more than once.
I wonder if the problem could be drive train related. Torque converter or transmission?
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Rusty
Dodge Dakota
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2/14/2003
14:18:14
| RE: 4.7 help
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Sure... Drivetrain. I would say the same thing if I was the mechanic who screwed something up. "It's nothing I did, its gotta be something else".
The torque converter and tranny were fine before, right??
I'm sure the answer is in Duners response. I would also start doing my own work or find a new mechanic.
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azdak
Dodge Dakota
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2/14/2003
18:20:42
|  RE: 4.7 help
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the pistons are not a concern the volumn of air is. its called volumetric efficiency with lower comp pistons there is more room to put more air = more hp here try this Pressure Ratio:(boost pressure + atmospheric pressure)/atmospheric pressure(10 psi boost + 14.5 psi)/14.5 = 1.7
Air Flow(lbs/min): This is the air flow you calculate based on engine displacement, boost
level, volumetric efficiency(VE),rpm How do I figure out the Air Flow of my engine? This is complex, basically to simplify this to calculating theoretical volumetric efficiency.
VE=(792001.6*(RWHP/0.83))/(RPM * Displacement in in3 * AP * CR)Where:
VE = Volumetric Efficiency (Theoretical)
RWHP = Rear Wheel Horse Power
Displacement in in3= Engine displacement in cubic inches (2.0L = 122 in3)
AP = Atmospheric Pressure (~14.5 psi depending on altitude)
CFM=(122*RPM*VE%)/3456 CR = Compression Ratio (Static is close enough)
* The better the information plugged into the formula the more accurate the output.
Conversions: Lbs/min = 0.0756 x CFM
this will tell you what you should be pushing for air volume needed to be efficient boost pressure can be 10# at 20 cfm or 10# at 40 cfm the boost guage does not tell flow and is it possible the KB is designed for higher comp engine you are going from 9.5 to 8.1 cr thats a decrease of what roughly 15% but an increase of 15% of cyl volume. the 24# injectors my not be enough you are trying to fill more air space with an injector that im sure was intended for a higher comp engine in this setup with the current a/f ratio you are running it seems low 14.7 is optimal more fuel needed. i dont believe the stock pump will keep up im not sure if it comes in the KB kit either running it fat wont burn those nice pistons either im sure duner after thinking about it will probably tell you the same check the things he listed if you really want to pull those pistons out i will be more than willing to purchase them at a used discount price lol they will work really good for the needed vol. im lacking in my turbo dak. also remember that when you are not on boost the vehicle will run like an 8.1 motor so power will be low till you are on the boost thanx for listening to my rant
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