Crank sensor position? - Page 2 - Off-Road Forums & Discussion Groups
Jeep-Short Wheelbase All discussion of short wheelbase Jeeps: CJ, TJ, YJ and JK

LinkBack Thread Tools Display Modes
post #11 of (permalink) Old 09-14-2005, 09:47 AM
Join Date: Sep 1999
Posts: 5,383
Thanks: 0
Thanked 1 Time in 1 Post
Re: Crank sensor position?

MAN! This board HAS come a long way!

Cal. still does the idle and fixed rpm thing for emissions testing don't they?

Intake restrictions are designed in to keep port velocities up and keep emissions down in idle.
Larger air filter area and/or less restriction is cheap horse power.

Same for restrictions on the exhaust.
Designed for emissions at idle and emissions at rpm.
Better flow will reduce back pressure, but might increase 'Draft' and 'Cylinder Scavenging'.
The trick is to scavenge all the exhaust from the chamber, with out loosing any of the incoming charge mixture to the scavenge...
That causes unburned hydrocarbons in the exhaust mix, and will cause a slightly lean condition, further screwing with emissions...

Put on a 'Sewer Pipe' exhaust and you may have problems with lean condition at rpm during emissions tail pipe testing.
I don't think you have enough flow for draft to affect at idle.

Like you said, less restriction in the intake tract (air filter) can often be felt in the seat of your pants. Most people, and factory vehicles, have WAY too small of air filters...
I'm not much on K&N, but they are a lot of good low restriction air filters out there, or you can just increase filter surface area.

Now you have the sucker breathing, what's next!?!
Junk Yard Genius is offline  
Sponsored Links
post #12 of (permalink) Old 09-14-2005, 10:15 AM Thread Starter
Way Outta Control
Join Date: Sep 1999
Location: usa
Posts: 10,815
Thanks: 0
Thanked 1 Time in 1 Post
Re: Crank sensor position?

All true.
The larger throttle body might make a change, but only at the top end - if that's what's restricting it now. The larger exhaust like I've put on handles the bigger flow now - or should. The limiting factor might be the cat - it's still the original. But a vacuum gauge tells me the exhaust is not doing the limiting.

When I put on the lower restriction air filter - snout and K&N - it not only made a difference at top end, but helped considerably mid range too - 2200 - 3500 R's. So stock obviously that was the "choke factor."

I was thinking playing with the crank sensor might affect ignition timing. The way it "feels" is it needs less advance under load. If it was a "old style" system I'd start there now. I'd twist the distributor down a bit to see if that helps, or disconnect the vac advance to put it down on the power curve.
It's not pinging, but less advance under load at midrange gets it down on the "torque curve," rather than the "efficiency curve." Right now I think the ECM is "pushing" the advance as far up as possible all the time.

I'm wondering if I can "trick" the ECM into backing down the timing a bit through the knock sensor input.

Is there a device now that can reprogram the ECM advance curve on these? I know there is for the older ECM's, but I think this one is different. '03 Rubicon - Direct ignition rather than the single coil units.

Last night I was heading west out of Palm Springs into a stiff headwind. I was down to 35 MPH several times - in 3rd gear - and barely holding! Trucks were passing me! Downright embarrassing!

I know the 35's don't help, but big trucks? I didn't want to run it at 5K, so more midrange "poop" would have helped.
There has also been a few sand dunes where it would be nice to have a few more ponies too.

Thanks for all the inputs.
RRich is offline  
post #13 of (permalink) Old 09-14-2005, 10:47 AM
Posts: n/a
Re: Crank sensor position?

Aaron...regarding emissions testing in CA...they did away with the idle...they now put it on a dyno and run it at 25 and 40 MPH for testing. More like real world...

It's all a classic case of the sum not exactly being equal to the parts.....

Reminds me of when I had (in a younger life) a 67 Camero RS conv with the ol' 327.
Had headers on it (to go along with the FI heads)...ran good...sounded even better with the caps pulled off (you didn't hear the exhaust leak). With a 4.56 rear end, I was doing 13.21 in the quater...not bad in those days. Got tired of the exhaust leaks and put stock Corvett cast iron manifolds on it....along with a good 2 1/4" dual exhaust. I never got around to timing it in the quater, but it 'woke' up the engine. Not only did it sound better, but I have much more low and mid range performance. I would give my left nut to have that car back......
Sponsored Links
post #14 of (permalink) Old 09-14-2005, 05:26 PM
Keyboard Implanted
NIX's Avatar
Join Date: Mar 2003
Location: Holland
Posts: 2,779
Thanks: 0
Thanked 1 Time in 1 Post
Re: Crank sensor position?

That's easy to say in your case. You allready took care of your offspring...
NIX is offline  
post #15 of (permalink) Old 09-14-2005, 09:44 PM Thread Starter
Way Outta Control
Join Date: Sep 1999
Location: usa
Posts: 10,815
Thanks: 0
Thanked 1 Time in 1 Post
Re: Crank sensor position?

He He - California has two different types of testing - still. It'll change someday.

In the more populated areas they use a dyno - at two speeds. Depending on weight - measured right on the dyno - it loads the vehicle down during testing - anywhere from 20 to 60 or so HP. That's to simulate "on road conditions." That also tests the NOx emissions, NOx isn't really produced till it's under load.

Then there's the "not so populated areas," like where I live in the desert. We still test at two speeds, but not loaded on a dyno - they call it idle, but - one test is at curb idle, the other is at midrange. It's done unloaded.

Virtually the same test all Calif used before the loaded mode testing started. We don't have to test - or fail, for NOx.

No, you cannot bring your car out here to have it smogged unloaded - the address where it's registered determines how it's tested, no matter where you get it tested.

What else would you expect from a "dual standard" state?

I had the opportunity to be part of the smog laws, the writing and creating them. I did some lobbying too. Without the people I was working with things would be really bad. Some politicians wanted to make it so any car older than 10 years would have to be crushed! Car clubs, parts houses etc all banded together to stop that crap! It barely worked.

I said the "opportunity?" Yup, I saw how "the system" worked. Bribes, under the table payoffs, extorsion, threats, all kinds of crooked stuff.

That's why I'm so down on politicians. They all should be drowned!
RRich is offline  
post #16 of (permalink) Old 09-14-2005, 09:48 PM Thread Starter
Way Outta Control
Join Date: Sep 1999
Location: usa
Posts: 10,815
Thanks: 0
Thanked 1 Time in 1 Post
Re: Crank sensor position?

Back to the topic - sorry.
If I can't get to the timing curve I suppose my next step would be ratio rockers. A lttle more lift with the same duration should help in the mid range and up, where it's needed the most.

But - not sure If I can find them, or I'll have to make them.

RRich is offline  
post #17 of (permalink) Old 09-15-2005, 04:29 AM
Join Date: Feb 2004
Posts: 946
Thanks: 0
Thanked 0 Times in 0 Posts
Re: Crank sensor position?

I would be suprised if DC doesn't have them.
John_Strenk is offline  
post #18 of (permalink) Old 04-26-2006, 10:34 AM
Keyboard Implanted
GeeAea's Avatar
Join Date: Sep 1999
Location: Pottstown, PA
Posts: 2,076
Thanks: 0
Thanked 1 Time in 1 Post
Re: Crank sensor position?

That's my take on it, LEVE. A bigger throttle body, except perhaps at WOT, only "simulates" more power due to the fact that every advancement of your foot on the pedal gives a bigger opening sooner. Airflow and MAP readings are indifferent to throttle opening. In closed loop I imagine that there may be some slight effect due to a different TPS reading ..but, as you said, the O2 is going to trump all of it in either mode eventually. Even in open loop if the system sees too many rich conditions, it will increment the pulse width narrower to reduce them.

Spacers are supposed to alter where the "sympathetic" pulsations occur inside the intake manifold. The flow is not constant ..but a series of pulses. When the momentum of the air flow slams against a closed valve, it creates a sonic shock wave back up the runner. This collides with other shock waves and is sent back down the runner. In a certain "range" ..these shockwaves are timed to add more air to the cylinder ..increasing volume metric efficiency.

That's how variable intake designs work. This is just a "fixed" mod ..hence it can only work in one narrow range. I would not bother.
GeeAea is offline  
post #19 of (permalink) Old 04-26-2006, 01:42 PM Thread Starter
Way Outta Control
Join Date: Sep 1999
Location: usa
Posts: 10,815
Thanks: 0
Thanked 1 Time in 1 Post
Re: Crank sensor position?

Good explanations - especially about the intake "shockwaves" as you call them. Essentially that's the same principle as the exhaust.

So far - on mine:
I put on a less restrictive muffler - not because of this, but the main reason was to get more room under it (04 Rubicon 4.0) for the suspension and mods. It eliminated probably 50 pounds too! The stock one is really big and heavy.
Performance increase was very slight, if any.

Throttle body spacer: About the same change in performance as changing the color of my shirt. Took it off.

Ditching the stock air box has made a significant difference. So far it's the only thing that's really been noticeable. At low R's and up to lower mid range no change, but around 2000 RPM under load it did. At WOT under hard load it's definitely better. Try it - just take a ride around the block with it disconnected - you'll see if it will help yours or not.

Variable MAP sensor - I used a switch to increase the signal voltage to the ECM. I could toggle it in and out.
On normal loads it made 0 difference. Increasing voltage simulates that it's under a heavier load than it really is.

Yes, the O2 sensor will counteract it, but it takes a reaction time to do it. First it has to richen the mixture before the O2 drops (but the richer mix has already passed through the engine,) then the ECM has to react and shorten the pulse widths to the injectors.
That all takes a second or two. But - during that second or two, if the limiting power factor (choke effect as it's being called here) there would have been a noticeable increase in power, even if only temporary. None noticed.

But - I know it did have an effect and how long it takes to react - when toggling back to normal voltage, after the O2 had told the ECM it was too rich and compensated for my false input - now it goes too lean for a moment. It would almost stall during the second or so recovery time.
So I know it was richening it.

In WOT up a steep hill it made 0 difference. Yes, the O2 normally would compensate for the false signal, but at WOT throttle (told to the ECM by the TPS) it ignores O2 readings - it's in open loop for that time.
No noticeable increase in power.

Mid range under load it reacts like at idle - including the "recovery" stall like at idle.

Still, the false signal did not increase power enough to notice, but toggling back to normal made it try to stall from going lean an instant was just like before.

There was a possible reason why the variable MAP showed no effect, that would have been if the ECM just did not have the capability of lengthening the pulse length, or the fuel system was not capable of giving more fuel. So the possibility exists it's a lack of fuel delivery problem. Higher volume pump, larger injectors etc would help in that case. But there is a way to verify it's a lack of fuel too:. Propane.

As you all know, propane is a hydrocarbon fuel - it can be added to the system easily with a hose and a valve. Running a hose to the front, right into the intake airstream - the PVC breather - is easy.
I could add fuel, as much as I wanted. As more propane is added, the O2 sensor commands the ECM to shorten the pulse widths, eventually the system runs on the propane, gasoline provided by the normal system becomes minimal. This can be done at idle or whatever speed desired.

Mid range - richening it - if it really was too lean - it would give an increase in power - even though temporary. No effect.
WOT - same thing - no effect.
At WOT under heavy load it's in open loop, so the O2 sensor has 0 influence. So adding the propane only serves to increase the richness. Propane could be added until a noticeable DECREASE in power existed - indicating lack of available fuel has has not been the ”choke.”

In fact, it reacted just like the variable MAP did.

Increasing the bore on the throttle body would help only at WOT where the added area would be used. The ECM and fuel system can most likely provide enough fuel to feed the extra air. But, I'd rather have an increase in mid range, that would make 0 difference at that speed.

So - that leaves either the intake - such as manifold, or the exhaust system. Being in California I cannot do much that can be seen. Increasing power and efficiency should not drive emissions up, but since laws say modifications cannot be done - even if they make it cleaner, it's a problem.

The next step would be camming - changing cam timing does not actually increase or decrease power very much per se. What it does is move the peak of the torque curve up or down RPM wise. It can make a significant difference if the rest of the system has a different peak (breathing, ignition timing etc) - getting all the peaks together really makes a big difference.

But - recamming can increase breathing - if that's the limiting factor now. Increasing duration or overlap can, and will have a profound effect (negative) on emissions. So that's out. Plus the fact that the system is using a MAP causes problems too. Much increase on duration or overlap really gets the intake pulsing - drives the poor MAP crazy!

But, more lift can be added as long as it's kept within reason. More mixture can be ingested. The simple and easy way for that is increasing the rocker ratios. Even that causes more pulsing, but not near as much as the other way.

So far I haven't found ratio rockers for the 4.0 - but I haven't really tried either - yet.

I was hoping there would be a little “trick” that could be done to increase drivability power. It seems like the engineers have done a great job optimizing it as it is, leaving not much more room for improvement. Especially considering the fact they have to keep emissions down and satisfy all the greenies in their VW busses!
RRich is offline  
post #20 of (permalink) Old 04-28-2006, 10:08 PM
Can't Get Enough
Join Date: Sep 1999
Location: Cotopaxi, Colorado
Posts: 1,036
Thanks: 0
Thanked 0 Times in 0 Posts
Re: Crank sensor position?

Enemerator learned? Modifing the position of the crank sensor on your 4.0 won't do much, as the programmed spark timing is already at the edge of detination and mostly beyond.

Modifing M.A.P. voltages will do nothing. At start-up, the PCM checks the voltage to correct for altitude. If changed during run time, the long term adaptives will correct up to 33%.

Time to learn assembly language, software issues.
dorfs is offline  
Sponsored Links

Quick Reply

Register Now

In order to be able to post messages on the Off-Road Forums & Discussion Groups forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:


Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

For the best viewing experience please update your browser to Google Chrome