Help!! getting ready to dyno my rt4wd!

northwest_war_wagonnorthwest_war_wagon Senior Wagonist
in Engine & Drivetrain
hey guys i need some help im almost done with my d16z6 turbo set up, only days away from needing dyno tunning so how do i do it! :( ? do i do it in 4wd on an all wheel drive dyno? or shut it off and do it on a front wheel drive dyno? wich way is best to get the most accurate whpand less likely to damage my tranny? thanks alot for all your help guys!
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Comments

  • Tatty90EE4Tatty90EE4 Wagonist
    i've never dyno'd a car but with the RT's i would think you'd need to do it with the 4wd on so you don't hurt the tranny.... besides i didn't know you could turn it off and still drive the car!! :?
  • HaydzHaydz Moderator
    Some people on here drive their cars permanently in 2WD. No idea if that is safe or not.

    I'd suggest 4-wheel dyno just to make sure.
  • noahrexionnoahrexion Wagonist
    As we all now we are primarily 2wd cars and when the fronts aren't spinning (they won't be loosing traction on the dyno roller) the rears aint' either. Because of this the 2nd roller (for the rears if you use a 4wd dyno) will just drag as it won't be powered (though it'll spin from the power the front is putting down).

    Either is fine actually and the only real advantage to the 2wd dyno (so long as its a dyno dynamics than its as good as you can get anyway) is that it may be cheaper hourly rate on a 2wd.
  • HaydzHaydz Moderator
    I honestly wouldn't trust it running only the fronts but with the 4WD engaged. There's just too much chance that the VC might decide to send a bit of power there. Would be pretty funny seeing a giant fan, a dynomometre and a Wagon all mated together though. Wee mechanical babies.
  • northwest_war_wagonnorthwest_war_wagon Senior Wagonist
    i was going to shut the 4wd off and just go fwd i don't think it would be that bad on it! would it!? this sucks! i just don't think a 4wd dyno would be acurret on hp cus the back wheels arent pushing at all times does that make sence?
  • SiWagonSiWagon Council Member
    This topics been covered. :?
    Yes u can run it in 2WD!When u disengage the 4WD.All it does is disengage the gear to the rear.If u look at exploded views of the 4WD tranny you'll see what I mean.
  • evol911evol911 familEE
    I told you this already... Disenage 4wd if thats what you want to do. No power will transfer past the transmission. You are not going for a max HP run, your runs should just be for tuning.

    I would dyno in 4wd though, it would be more accurate. You are carrying around all the weight for the 4wd anyways, might as well let the back wheels do some pushing on the dyno. I don't think it would be logical to say you WHP in 2wd is what you car is running. Everytime you spin the tires and your rears hook up you will probably take a hit to your WHP. After its tuned, I would find out what the WHP is with 4wd engaged and thats the WHP I would go with.

    And 4wd is not going to make your engine run lean or rich!!!! :lol: :lol: :lol: <
    WRONG

    And how the 4wd works on our cars:
    If the driveshaft from the transmission to the Viscous Coupler spins any speed different then the driveshaft coming from the rear diff to the Viscous Coupler, the VC engages. Once start spinning those front rollers and the rear rollers of the dyno arent spinning the same speed, the VC will engage and you will be in 4wd. Something I just thought of though, if the speed of which the rear rollers coast to a stop is different than the front rollers that might keep your VC engaged. Maybe I'm wrong by saying that force on the rear wheels can drive the 4wd all the way up to the transmission. <
    WRONG
  • noahrexionnoahrexion Wagonist
    evol911 wrote:
    I told you this already... Disenage 4wd if thats what you want to do. No power will transfer past the transmission. You are not going for a max HP run, your runs should just be for tuning.

    I would dyno in 4wd though, it would be more accurate. You are carrying around all the weight for the 4wd anyways, might as well let the back wheels do some pushing on the dyno. I don't think it would be logical to say you WHP in 2wd is what you car is running. Everytime you spin the tires and your rears hook up you will probably take a hit to your WHP. After its tuned, I would find out what the WHP is with 4wd engaged and thats the WHP I would go with.

    And 4wd is not going to make your engine run lean or rich!!!! :lol: :lol: :lol:

    And how the 4wd works on our cars:
    If the driveshaft from the transmission to the Viscous Coupler spins any speed different then the driveshaft coming from the rear diff to the Viscous Coupler, the VC engages. Once start spinning those front rollers and the rear rollers of the dyno arent spinning the same speed, the VC will engage and you will be in 4wd. Something I just thought of though, if the speed of which the rear rollers coast to a stop is different than the front rollers that might keep your VC engaged. Maybe I'm wrong by saying that force on the rear wheels can drive the 4wd all the way up to the transmission.

    To bad an awd dyno doesn't work that way. The rollers are constantly matched; you could put a 2wd car on a 4wd dyno and as long as your e brake wasn't on your rear would turn at the same speed as your fronts cause they are linked via another.

    2wd driving and dyno tuning is fine; I cannot imagine any ill side effects running 2wd pull after pull after pull for power or tuning... it doesn't matter. The trans can still hold the same amount of power regardless of whether or not its in 4wd mode. Furthermore, a properly hooked up car shouldn't really be spinning too much and you would thus be 2wd anyway. When/if any time you are spinning and the rears kick in you won't notice much difference in power anyway, it will be as seamless as the transition from 2wd to 4wd is.
  • evol911evol911 familEE
    Didn't know dyno rollers were matched on a 4wd dyno and now that I think about it, I don't know why that didn't click in my head. I was thinking you could run a fwd or awd or rwd on a 4 wheel dyno because the rollers just free-wheeled. My mistake. :oops: And also my mistake if I anyone got the impression that I meant tires losing traction on the dyno rollers. I meant losing front tire traction on the street. When I said spinning the front and rear rollers I meant simply turning them.
  • JakerJaker familEE
    A 4wd car will load the motor a lot more heavily than a 2wd (especially FWD) car. This will lead to the need for more fuel. So yes, a 4WD will run leaner for the same engine settings than a 2wd. Look at the Epic Tuning hatch. They bent 2 of (maybe it was all 4) rods in that motor once they went 4WD. That can be attributed to the motor running a little more lean, and the extra loads that the additional "traction" was putting on the motor.
  • evol911evol911 familEE
    My mistake again on the 4wd leaning out the engine. :oops:

    So can someone at least agree with me that to get the best tune and realistic numbers, it should be run 4wd????
  • shenrieshenrie Council Member
    No awd dyno here.

    I forgot about the lever on the tranny and always just dynoed mine with the bolts out of the driveshaft.
  • StockStock Wagonist
    4WD so you know the load is as close to actual street driving as possible.
  • Shaun KShaun K Wagonist
    Stock wrote:
    4WD so you know the load is as close to actual street driving as possible.
    Except there's no guarantee that you'll be driving the rear wheels at all when on the dyno. In fact I'd bet that it would automatically run in 2WD mode on any dyno, unless you pour water on the front rollers :lol:
  • northwest_war_wagonnorthwest_war_wagon Senior Wagonist
    Shaun K wrote:
    Stock wrote:
    4WD so you know the load is as close to actual street driving as possible.
    Except there's no guarantee that you'll be driving the rear wheels at all when on the dyno. In fact I'd bet that it would automatically run in 2WD mode on any dyno, unless you pour water on the front rollers :lol:

    so i should still disconnect the 4wd to be safe right?
  • evol911evol911 familEE
    Shaun K wrote:
    Stock wrote:
    4WD so you know the load is as close to actual street driving as possible.
    Except there's no guarantee that you'll be driving the rear wheels at all when on the dyno. In fact I'd bet that it would automatically run in 2WD mode on any dyno, unless you pour water on the front rollers :lol:


    But you are carrying around the extra weight so might as well make use of it.
  • evol911evol911 familEE
    Dyno it in 2wd and 4wd and tell us what the difference is with the numbers!!!!!!!
  • northwest_war_wagonnorthwest_war_wagon Senior Wagonist
    evol911 wrote:
    Dyno it in 2wd and 4wd and tell us what the difference is with the numbers!!!!!!!
    yea! let me dyno my car twice just for fun!
  • StockStock Wagonist
    This is the kind of shit that keeps me street tuning on abandoned roads. Tuning for real load conditions FTW.
  • evol911evol911 familEE
    northwest_war_wagon wrote:
    evol911 wrote:
    Dyno it in 2wd and 4wd and tell us what the difference is with the numbers!!!!!!!
    yea! let me dyno my car twice just for fun!


    Do you think you're only gonna do one run and have all the kinks worked out? You might be there for hours do numerous pulls, it'll take you couple minutes to switch it between 2wd and 4wd.
  • Shaun KShaun K Wagonist
    Where are you dynoing? RRev only has a 2-wheel dyno.
  • northwest_war_wagonnorthwest_war_wagon Senior Wagonist
    Shaun K wrote:
    Where are you dynoing? RRev only has a 2-wheel dyno.

    rrev or vip not sure yet
  • HaydzHaydz Moderator
    You guys are all wrong about running it in 4WD mode but only running a FWD dyno.

    If there is a difference in rotation speed between front and rear, it sends power to the rear. If the rear is sitting on concrete what will happen?

    The wagon is going to do one of three things...
    -break traction in the rear to keep up
    -push itself right off the dyno
    -fuck your transmission and vc because of the massive load it all of a sudden has to try and push

    As far as i'm concerned there's only one way to do it - 4WD dyno with 4WD engaged. That was you'll also defeat the mentioned lean out issues.
  • shenrieshenrie Council Member
    Haydz wrote:
    If there is a difference in rotation speed between front and rear, it sends power to the rear. If the rear is sitting on concrete what will happen?

    And if it was on speed matched rollers on the awd dyno, how is the coupler/diff gonna act? I would imagine that as long as you dont break traction its going to stay in fwd mode the entire time since the rear wheels are going the same speed as the fronts.

    What I would be worried about is it what happens if the car breaks traction in front? If the drums speed up to the catch up with the fronts and engage the rears youll have a heavy weighted drums fighting your diff/couplers. Just seems to me that since the awd isnt constant, that the rear wheels would be somewhat fighting the drums. Id hate to see any damage happen as a result cause the heavy ass drums arent going to give like the diff and couplers will. Hell I dunno, I could be way off here, but I thought Id mention what came to mind.

    When I did my car the first time I had free acces to a dyno. The car was setup OBD1 and I had a chrome program for the valvetrain I installed. Put it on the dyno and the program was almost dead on with the exception of being just a tad fat at idle and just a tad lean at 8500+rpms. We dialed it in and moved vtec around till we had the magic combination of what looked best on paper. Then I hooked the driveline (CRV tranny) back up and put a wideband on it and went out in the real world to fine tune it with a AFC. The car on the street with all four wheels engaged had almost the same readings as the car on the dyno in fwd mode. We had to take out a little more fuel down low, but other than that, it was right on the money.

    Another thing that came to mind is even though the car will have more load on it in awd, the only real time your going to be using it is off the line where youll have your rms up anyway. If the rpms are up and your in launch mode, I cant see it going lean enough with the extra load to affect anything when your that high in the rpms anyway. Again, I could be off here. Just throwing out ideas.
  • noahrexionnoahrexion Wagonist
    shenrie wrote:
    Haydz wrote:
    If there is a difference in rotation speed between front and rear, it sends power to the rear. If the rear is sitting on concrete what will happen?

    And if it was on speed matched rollers on the awd dyno, how is the coupler/diff gonna act? I would imagine that as long as you dont break traction its going to stay in fwd mode the entire time since the rear wheels are going the same speed as the fronts.

    What I would be worried about is it what happens if the car breaks traction in front? If the drums speed up to the catch up with the fronts and engage the rears youll have a heavy weighted drums fighting your diff/couplers. Just seems to me that since the awd isnt constant, that the rear wheels would be somewhat fighting the drums. Id hate to see any damage happen as a result cause the heavy ass drums arent going to give like the diff and couplers will. Hell I dunno, I could be way off here, but I thought Id mention what came to mind.

    When I did my car the first time I had free acces to a dyno. The car was setup OBD1 and I had a chrome program for the valvetrain I installed. Put it on the dyno and the program was almost dead on with the exception of being just a tad fat at idle and just a tad lean at 8500+rpms. We dialed it in and moved vtec around till we had the magic combination of what looked best on paper. Then I hooked the driveline (CRV tranny) back up and put a wideband on it and went out in the real world to fine tune it with a AFC. The car on the street with all four wheels engaged had almost the same readings as the car on the dyno in fwd mode. We had to take out a little more fuel down low, but other than that, it was right on the money.

    Another thing that came to mind is even though the car will have more load on it in awd, the only real time your going to be using it is off the line where youll have your rms up anyway. If the rpms are up and your in launch mode, I cant see it going lean enough with the extra load to affect anything when your that high in the rpms anyway. Again, I could be off here. Just throwing out ideas.

    Actually you are right on the money; not only is it crazy to me to think that once the "4wd kicks in yo!" that your car will lean out and cause problems; but you definitely will be running two rollers with only two wheels if you run on a 4wd dyno.

    If you DISengage 4wd from the lever near the speedo; you will NOT be putting power out the rear: thus you will NOT send any "message" to the VC to kick anything back to the rear wheels. Definitely do not run your car on a 2wd dyno without disconnecting 4wd first. You can verify 100% that it is disengaged if the output shaft is NOT spinning. Your car is totally fine to dyno on a 2wd dyno if you do this.

    Like I said before, if you dyno on a 4wd dyno you will NOT be spinning/loosing traction on the rollers (unless you are making some stupid power) THUS the rears will not have ANYthing sent back to them. The rollers coincide with one another so your rear will be spinning the same AND your fronts will be the ones powering BOTH rollers (more load on the front that is 99% the case when you will be driving on the street).
  • northwest_war_wagonnorthwest_war_wagon Senior Wagonist
    noahrexion wrote:
    shenrie wrote:
    Haydz wrote:
    If there is a difference in rotation speed between front and rear, it sends power to the rear. If the rear is sitting on concrete what will happen?

    And if it was on speed matched rollers on the awd dyno, how is the coupler/diff gonna act? I would imagine that as long as you dont break traction its going to stay in fwd mode the entire time since the rear wheels are going the same speed as the fronts.

    What I would be worried about is it what happens if the car breaks traction in front? If the drums speed up to the catch up with the fronts and engage the rears youll have a heavy weighted drums fighting your diff/couplers. Just seems to me that since the awd isnt constant, that the rear wheels would be somewhat fighting the drums. Id hate to see any damage happen as a result cause the heavy ass drums arent going to give like the diff and couplers will. Hell I dunno, I could be way off here, but I thought Id mention what came to mind.

    When I did my car the first time I had free acces to a dyno. The car was setup OBD1 and I had a chrome program for the valvetrain I installed. Put it on the dyno and the program was almost dead on with the exception of being just a tad fat at idle and just a tad lean at 8500+rpms. We dialed it in and moved vtec around till we had the magic combination of what looked best on paper. Then I hooked the driveline (CRV tranny) back up and put a wideband on it and went out in the real world to fine tune it with a AFC. The car on the street with all four wheels engaged had almost the same readings as the car on the dyno in fwd mode. We had to take out a little more fuel down low, but other than that, it was right on the money.

    Another thing that came to mind is even though the car will have more load on it in awd, the only real time your going to be using it is off the line where youll have your rms up anyway. If the rpms are up and your in launch mode, I cant see it going lean enough with the extra load to affect anything when your that high in the rpms anyway. Again, I could be off here. Just throwing out ideas.

    Actually you are right on the money; not only is it crazy to me to think that once the "4wd kicks in yo!" that your car will lean out and cause problems; but you definitely will be running two rollers with only two wheels if you run on a 4wd dyno.

    If you DISengage 4wd from the lever near the speedo; you will NOT be putting power out the rear: thus you will NOT send any "message" to the VC to kick anything back to the rear wheels. Definitely do not run your car on a 2wd dyno without disconnecting 4wd first. You can verify 100% that it is disengaged if the output shaft is NOT spinning. Your car is totally fine to dyno on a 2wd dyno if you do this.

    Like I said before, if you dyno on a 4wd dyno you will NOT be spinning/loosing traction on the rollers (unless you are making some stupid power) THUS the rears will not have ANYthing sent back to them. The rollers coincide with one another so your rear will be spinning the same AND your fronts will be the ones powering BOTH rollers (more load on the front that is 99% the case when you will be driving on the street).

    sweet! thanks for the info!
  • noahrexionnoahrexion Wagonist
    BTW, before when you had your car listed for sale my brother looked at your wagon in Portland; he said it was stupid clean. I've always liked your wagon, good work with it and good luck with the turbo setup, I am sure it will be as kick ass as the rest of the work done to yours (clean, OEM).
  • northwest_war_wagonnorthwest_war_wagon Senior Wagonist
    noahrexion wrote:
    BTW, before when you had your car listed for sale my brother looked at your wagon in Portland; he said it was stupid clean. I've always liked your wagon, good work with it and good luck with the turbo setup, I am sure it will be as kick ass as the rest of the work done to yours (clean, OEM).

    lol thanks bro yea i ordered 2 inercooler pipping kits just to make sure it looks clean
  • curtcurt Wagonist
    so isn't it like a 90/10 split front to back until the front slips? I think you would be fine in 2wd mode.
  • JakerJaker familEE
    There is no drive/torque sent to the rear wheels unless the fronts are slipping. In theory if the fronts were slipping 100%, the rears would have 100% of the torque. There is no torque split per se. If the fronts were slipping 50%, then 50% of the torque would go to the rear wheels. If it was 20% slip at the fornt wheels, then 20% would go to the rear wheels. Its a mechanical system. There is no electronic wizardry "distributing" torque.

    Based on the gear ratios, the fronts can only slip 0.12% (yes that's right, less than 1%) before the viscous coupler starts to lock.
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