B9B Swap...acting funny....

[Axianator]

AutoSHO:
No, on both counts. The flywheel absolutely, positively, 100% has nothing to do with the rev limiter programmed into the engine computer.

Smaller tires will make the speedo faster than the car is actually going, but it does not change the speed indicated at a given RPM. At 7300 RPM in third you are doing 106 mph.

I very sincerely doubt there is any SHO out there without a rev limiter that is completely stock. A chipped car can have no rev limit (bad, bad idea) but other than that, your car will be limited to 7300 rpms.

Ah, my good man, but the weight of a flywheel does have an effect on the rev limiter! As an example, I know of at least one local SHO owner who installed an 8lb. Fidanza flywheel on his '91 and, under the factory programming, his indicated rev limit was increased to at least 7800 rpms in first gear, possibly others. I've also heard of other SHO folk performing similar "upgrades" to their MTX's with similar results.

To back this statement, keep in mind that the primary method that the EEC uses to determine when the rev limiter should be activated is PIP. PIP is a sample rate frequency primarily used in timing calculations that lets the EEC know how fast the crank is turning per operating cycle ... if PIP is sampled less than x amount of times in a certain time frame (specified by the "Minimum PIP period" scalar in the EEC program), then the EEC limits RPM by introducing the rev limiter. By using a lightened flywheel such as the Fidanza, you can effectively raise the rev limiter a few hundred RPM's under the stock programming due to the lighter rotational mass allowing the engine to approach redline faster in certain gears. A majority of the time, the EEC won't begin to limit RPM until the engine has already exceeded the stock rev limiter point.

Clear as mud now? wink

As for "indicated speed", I'm assuming you are referring to the speed as indicated by the speedometer? If so, then yes ... by changing to a tire with a ratio other than stock, you can and will throw the speedometer readings off. How much the readings are thrown off will depend on the size and ratio of the tire that you upgraded to. Regardless, your indicated speed will be different than the speed that you are actually travelling.

<small>[ March 16, 2004, 12:37 AM: Message edited by: Axianator ]</small>

 

[AutoSHO]

The lightened flywheel will not change the acceleration of the Engine so much that the PIP resolution is too low to catch it. Maybe in neutral or while missing a shift, but not in gear, it is still gonna stop the motor at 7300 rpms. In gear the acceleration difference between the lightened and stock flywheels is not going to have a huge effect. I sincerely doubt the engine is actually turning over 7300 rpms.

 

[Axianator]

AutoSHO:
The lightened flywheel will not change the acceleration of the Engine so much that the PIP resolution is too low to catch it. Maybe in neutral or while missing a shift, but not in gear, it is still gonna stop the motor at 7300 rpms. In gear the acceleration difference between the lightened and stock flywheels is not going to have a huge effect. I sincerely doubt the engine is actually turning over 7300 rpms.

I have to disagree with you there, Chris. I'll admit that I could be wrong about the indicated RPM of the tach possibly not matching the actual speed of the engine. However, most people don't use as light of a flywheel as the guy in my example does (an ultra-lightweight 8lb'er Fidanza versus the typical 17lb SHO Shop special). It is entirely possible that a Fidanza will enable you to hit a higher RPM before the rev limiter kicks in. Heck, I've managed to pull off the same stunt (with less consistency, of course) in my ATX with the stock tranny and under the stock rev limiter (IIRC). Fact is, is that it is entirely possible to throw PIP readings off with a super-light flywheel and pass the factory rev limiter under the stock program.

 

[AutoSHO]

Well, I dont have any personal experience to back up my claim (I don't own one) but I have a very hard time believeing it changes the rev limit that much. I can see 50 or even 100 extra RPM because of the unexpectedly fast acceleration, but not 500.

If it was the case that any mod which increased the speed at which the engine approached redline caused the redline to be higher, how do cars with mods still stop at 7300? And if the car can catch the motor free revving at 7300, how is it not gonna stop it in gear at 7300?

 

[Axianator]

AutoSHO:
Well, I dont have any personal experience to back up my claim (I don't own one) but I have a very hard time believeing it changes the rev limit that much. I can see 50 or even 100 extra RPM because of the unexpectedly fast acceleration, but not 500.

If it was the case that any mod which increased the speed at which the engine approached redline caused the redline to be higher, how do cars with mods still stop at 7300? And if the car can catch the motor free revving at 7300, how is it not gonna stop it in gear at 7300?

As I, too, have stated, I could very well be wrong about that part of my statement. In support of my claims, though, I take you back to the flywheel statement that I just made. FWIW, I have been in the guy's car while he made a few trips to redline and the Fidanza defintely makes a difference in the way the engine responds. The amount of time it took to get to redline in the first couple of gears seemed significantly shorter and acceleration was definitely affected overall.

As for the modded cars in your example, most do not incorportate a flywheel as light as the Fidanza into their mod list. IINM, most people with a lightened flywheel who buy aftermarket go with a SHO Shop (type) 17-18lb. flywheel or just machine their own down to around that range. Even so, I don't think a flywheel that's just a few pounds lighter than stock will have enough affect on PIP resolution to change when the rev limiter kicks in, whether it be free-revving the engine in neutral or running the car hard in gear. An 8lb. flywheel could, however, which is why I cited it as an example.

Again, if I'm wrong on any part of this, I will concede to it. I welcome other's opinions. wink

<small>[ March 16, 2004, 02:00 AM: Message edited by: Axianator ]</small>

 

[AutoSHO]

I agree that some of the modded SHOs out there dont hae a lightened flywheel, I was just using it as an example. Anything that increases the speed at which it heads for the rev limiter would cause it to change, if the 9 Ib'er does too.

I know it makes a big difference in how quick the car is in lower gears, because of the rate of acceleration. I just dont think I can accept the fact that the rev limiter is truly moved higher. I can see how the tach needle might get "thrown" further since the engine is gaining speed at a faster rate, but the true rev limit, IMO, is still gonna be the same at 7300.

 

[Axianator]

AutoSHO:
I agree that some of the modded SHOs out there dont hae a lightened flywheel, I was just using it as an example. Anything that increases the speed at which it heads for the rev limiter would cause it to change, if the 9 Ib'er does too.

I know it makes a big difference in how quick the car is in lower gears, because of the rate of acceleration. I just dont think I can accept the fact that the rev limiter is truly moved higher. I can see how the tach needle might get "thrown" further since the engine is gaining speed at a faster rate, but the true rev limit, IMO, is still gonna be the same at 7300.

Well, as should be the goal of any good debater, you've forced me to study this issue further, Chris. Now see what you've done?!

Considering how fast a supercharged car will accelerate in the lower gears, I'll see if I can't do some "research" with Murph's SC'ed beast sometime in the near future (IINM, he has a Fidanza on his '92). Between the readings I get from my TwEECer datalogger and a seperate, external, more accurate tach, I should be able to find out how much of a difference the Fidanza actually makes on the stock rev limiter.

In the meantime, we've given everyone else some interesting reading material. wink

<small>[ March 16, 2004, 02:09 AM: Message edited by: Axianator ]</small>

 

[AutoSHO]

That we have

I really need to get some sleep. Doing a 120k Maint. and staying up late every night dont go together. I need to take an oil change and brush my timing belt... wait, that can't be right!

 

[NotSoSlowSHO]

I might just be stating the obvious here, so please humor me...

How in the world can a flywheel change the computer controlled rev limiter?

We are talking about CONTINUOUS revs, correct?
As in, in gear, reving til the limiter kicks in.
As apposed to free-reving, and allowing the rotating mass of the engines inernals to rev a bit beyond the limiter?

I mean, all the limiter does is start 'dropping' cylinders when 73XX rpm is reached. It does not physically limit rotation at that rpm.

Example: Miss a shift. Hit 2nd at 80mph, instead of 4th. The motor WILL rev beyond the limiter.

Or am i just talking out my **** shrug

 

[Axianator]

lol, I second the whole taking an oil change, err... I mean taking a shower!

Before I do that, though, I have to go nuke a frozen dinner. Can you say charbroiled beef strips and steak fries?

rofl

 

[Axianator]

NotSoSlowSHO:
I might just be stating the obvious here, so please humor me...

How in the world can a flywheel change the computer controlled rev limiter?

We are talking about CONTINUOUS revs, correct?
As in, in gear, reving til the limiter kicks in.
As apposed to free-reving, and allowing the rotating mass of the engines inernals to rev a bit beyond the limiter?

I mean, all the limiter does is start 'dropping' cylinders when 73XX rpm is reached. It does not physically limit rotation at that rpm.

Example: Miss a shift. Hit 2nd at 80mph, instead of 4th. The motor WILL rev beyond the limiter.

Or am i just talking out my **** shrug

Yes, I was referring to continuous revs while in gear. I didn't mean that the flywheel actually changed the rev limiter itself, rather that it caused the limiter to kick in at a higher RPM than what is otherwise indicated by the stock EEC program.

A typical 17lb. SHO Shop flywheel is about 5lbs. lighter than stock, yet many people within the SHO community who own and use one can tell you that it makes a noticeable difference in the way the car accelerates and revs, even while in gear. Now take an aluminum flywheel like the Fidanza that's even 10lbs lighter than the SHO Shop's and note how the engine responds. Under this type of scenario, I believe it entirely possible to affect PIP in such a way that the EEC will not think to limit RPM until a much higher RPM than normally indicated.

 

[DHMag]

ever driven faster than your headlights can illuminate the ground ? you can spin an engine faster than the EEC or any component of such can keep up.

the rev limiter on a Ford Ranger is controlled thru the VSS. by adding a resistor to this circuit, you can cheat the EEC and gain a higher rev limit.

 

[Markus]

DHMag:


the rev limiter on a Ford Ranger is controlled thru the VSS. by adding a resistor to this circuit, you can cheat the EEC and gain a higher rev limit.

I find this very hard to believe. Why, you ask? Read on...

1) The signal generated by the VSS is, depending on the vehicle, either an analogue sine-wave like signal or a train of digital pulses. The key here is that the EEC uses the frequency of the VSS generated signal to determine speed. The amplitude of the signal is ignored. Adding a resistor in no way changes the frequency.

2) If the rev limiter was based on the VSS, the EEC would have to know which gear the transmission is in. Why would anyone limit the revs using a combination of the above 2 sensors when the crank position sensor, by itself, already offers this data? Further more, if the VSS fails the EEC will not be able to limit the revs. This will result in engine damage. If the crank sensor fails the EEC simply shuts down the engine. Also, using the combination of VSS and transmission gear sensor means the rev limiter is dependent upon tire diameter.

 

[Axianator]

Markus:
I find this very hard to believe. Why, you ask? Read on...

1) The signal generated by the VSS is, depending on the vehicle, either an analogue sine-wave like signal or a train of digital pulses. The key here is that the EEC uses the frequency of the VSS generated signal to determine speed. The amplitude of the signal is ignored. Adding a resistor in no way changes the frequency.

2) If the rev limiter was based on the VSS, the EEC would have to know which gear the transmission is in. Why would anyone limit the revs using a combination of the above 2 sensors when the crank position sensor, by itself, already offers this data? Further more, if the VSS fails the EEC will not be able to limit the revs. This will result in engine damage. If the crank sensor fails the EEC simply shuts down the engine. Also, using the combination of VSS and transmission gear sensor means the rev limiter is dependent upon tire diameter.

Actually, Mark, assuming that the truck in question was an automatic and the resistor mod worked as described, then Dale would have a valid point here. Shift points on an automatic EEC-IV-controlled vehicle are determined by tables that are referenced first by throttle position and then by speed as indicated by the VSS. If the VSS was modified in such a way that it reported a speed lower than what you were actually travelling, then it's possible that the car would shift at a higer RPM (and speed) than it normally would with a properly functioning VSS.

 

[revhardSHO]

this flywheel rev-limiter mod must only work in 1st, MAYBE 2nd right?

 

[Axianator]

Most likely, although I'm not entirely sure. I'll have to check with the gentleman in question (MikeD of Hypercoat) to see when and in what gears the phenomenon actually works.

 

[Markus]

Axianator:

Markus:
I find this very hard to believe. Why, you ask? Read on...

1) The signal generated by the VSS is, depending on the vehicle, either an analogue sine-wave like signal or a train of digital pulses. The key here is that the EEC uses the frequency of the VSS generated signal to determine speed. The amplitude of the signal is ignored. Adding a resistor in no way changes the frequency.

2) If the rev limiter was based on the VSS, the EEC would have to know which gear the transmission is in. Why would anyone limit the revs using a combination of the above 2 sensors when the crank position sensor, by itself, already offers this data? Further more, if the VSS fails the EEC will not be able to limit the revs. This will result in engine damage. If the crank sensor fails the EEC simply shuts down the engine. Also, using the combination of VSS and transmission gear sensor means the rev limiter is dependent upon tire diameter.

Actually, Mark, assuming that the truck in question was an automatic and the resistor mod worked as described, then Dale would have a valid point here. Shift points on an automatic EEC-IV-controlled vehicle are determined by tables that are referenced first by throttle position and then by speed as indicated by the VSS. If the VSS was modified in such a way that it reported a speed lower than what you were actually travelling, then it's possible that the car would shift at a higer RPM (and speed) than it normally would with a properly functioning VSS.

But, as I originally wrote, the EEC uses the frequency of the VSS signal, not the amplitude. Adding a resistor will NOT change the frequency. Thus, the resistor mod will not work. Dale's original statement was that adding the resitor would, in effect, change the engine speed at which the rev limiter kicked in. He mentioned nothing about shift points.

<small>[ March 17, 2004, 08:44 AM: Message edited by: Markus ]</small>

 

[Axianator]

I understand and accept that. I was simply giving you a set of conditions that would have to exist for Dale's scenario to work ... if the vehicle was an MTX, I don't see how the VSS part of his statement could be true (although I'm very interested in hearing more from him about how this works). He never actually stated whether the Ranger was an MTX or ATX.

No need to get all defensive about it, man. wink

 

[Markus]

Axianator:
I understand and accept that. I was simply giving you a set of conditions that would have to exist for Dale's scenario to work ... if the vehicle was an MTX, I don't see how the VSS part of his statement could be true (although I'm very interested in hearing more from him about how this works). He never actually stated whether the Ranger was an MTX or ATX.

No need to get all defensive about it, man. wink

If I sounded defensive, I sincerely apologise. I did not intend to so do!

 

[Axianator]

No worries, Mark. thumb

Message boards are the worst when it comes to miscommunication sometimes. wink