What Does Ski-doo Dpm Do? [Archive] - Snowmobile World : Your #1 Snowmobile Forum

: What Does Ski-doo Dpm Do?


Dynamo^Joe
09-10-2003, 09:17 AM
Can anyone answer; What the heck does DPM do?

Does anyone have any actual facts "and not Heresay" on what DPM actually does?

Joe, the DPM does this...does that and also does this... "Knowwhatimean?

The clutch kit I make for the 800 RER [regardless of year/model] has been using about 18 grams total pin weight for all of the test exercises and just plain ol' trail riding.

For fun, got the race dept to disable the DPM and ever since it's been disabled, I've been adding weight and lowering the clickers just to get the rpm's down.

I really don't understand what the dpm does but it sure seems to mess with everything especially top end. :cussing:

mxzadr800
09-10-2003, 04:06 PM
Joe what year sled is the 800? It would interesring to see if there is a consistent gian when the DPM is yanked. Adding weight and adj. clickers makes me think some real noticeable gains have occured. Have any numbers or time gains to show the improvement? I have a 02 800 and I have been thinking about yanking the DPM.

purple punisher
09-10-2003, 06:34 PM
if you got the race dept to unhook then ask them exactly how or what affects it. It does work off float bowl pressure..........but does that mean that its altitude or barometric pressure affecting more than temp or what about humidity. Maybe in the summer it over compensates. Doesn't help you but gives more questions to answer

Hoosier Daddy
09-11-2003, 12:38 AM
Have seen the same gains. Took dpm off and sled pulls more rpm. You can feel thedifference in power.

SummitAK
09-11-2003, 04:20 AM
The DPM system is only supposed to vary the fuel delivery to the carburetors based on changes in temperature and barometric pressure. The Doo specs are 3000+ rpm, -4F+ and 1000mBar, or less, atmospheric pressure for DPM activation. DPM compensation only varies fuel delivery by applying a vacuum to the carburetor float bowls using carb venturi vacuum controlled through the DPM manifold with a solenoid. Since only a vacuum is involved (on ZX Doos) the DPM can only lean the fuel delivery. Removing the DPM should only allow the sled to run the baseline jetting that is currently installed.

Joe did you lean the jetting after DPM removal? or did the Doo race guys install leaner jets?

What did they disconnect to disable the DPM? Only vacuum lines or did they disconnect electronics? Maybe there is additional compensation in the DPM system that is not published? - timing advance curves?

SummitAK

dooman
09-11-2003, 06:27 PM
Originally posted by purple punisher@Sep 10 2003, 04:34 PM
Maybe in the summer it over compensates.
I will say what I have learned about the dpm system is just as summit ak stated.only I will add that above 40 f it is not active.

dunittoo
09-12-2003, 12:22 AM
The DPM is as Summitak says but on the 03 models in particular and maybe other models as well, there are 2 other wires that come from the temp sensor and join the dpm wires that go to the mpem. That tells me that the temperature of the engine must be effecting either the timing or the carbs or both.
DPM only effects the float bowl pressure but there are other things tied into the mpem that are effecting the dpm and timing, I am 99.9 % sure of that. AND THAT IS A CLUTCHING NIGHTMARE.

hillpounder
09-12-2003, 02:59 AM
I'm not saying that it can't happen but I've played with the temp and baro sensors and saw no timing change on my strobe. Moved the temp sens from cold to hot water and sucked and blowed on the baro tube, no change. But engine wasn;t under load and maybe the mpem knew that. One little known feature of the mpem is a something that works like a throttle position sensor. By timing the acceleration of the crank it knows whether you are on or off the throttle. This feature does make timing changes. This MAY make it hard to do timing curve checks unless the engines is under load. As far as I can tell the dpm feature is independant of the timing. I can see where it would be possible to use the dpm to bring on a rich failsafe condition based on coolant temp? The wiring diagrams I've looked at show the temp sensor only tied to the idiot light, no mpem wiring. If you say there is another set of wires from the coolant sensor to the mpem I'd guess overheat protection using the dpm on dpm sleds, and possibly timing on non dpm? Since the move to DC on the new sleds I suspect doo has made some changes. I've found doo very tight lipped about the mpem, kind of a need to know basis. I'm not sure even the race shop guys really know alot about it? From what I've seen they just take some timing out of the midrange, extend advance a little on top, and turn off the rpm limiter.

dunittoo
09-12-2003, 12:17 PM
Does anyone have a non dpm, 2003 600 or 800 that they can check? Look to see if there are 2 or 4 wires coming from the temp sensor.
Hillpounder, when you did your experiment did you have the sled on a stand so that you could get the rpm's up to 6000- 7000?

purple punisher
09-12-2003, 01:02 PM
The temp sensor will affect timing when the motor gets over 175 degrees. We have found that out on the asphalt.

BellevilleMXZ
09-12-2003, 04:52 PM
Originally posted by purple punisher@Sep 12 2003, 11:02 AM
The temp sensor will affect timing when the motor gets over 175 degrees. We have found that out on the asphalt.
Get back to work slacker :hallo1:

folgers
09-15-2003, 09:51 AM
REAL TIME TESTING
clutched
350 mains
stock pilots
un pluged dpm
heated the pipes like 6 to7 raps
out of the hole booooooooooooooogggggg some time went after like 200 feet!!
4 times in a row
chang pilots to 35 from 17.5
still a booooooog not as bad!

pluged the dpm, droped the sled in cold went 77 6.0 1.627 60 foot time!!

going foward
set the sled up heat the pipe up change nothing els and get 67 mph out of the sled the 60 foot time was less than above lost the slip :sly:
next 3 races droped it in "cold" just cooled down the block and stayed in the uper 70s!

Dynamo^Joe
09-16-2003, 03:00 PM
http://www.snowest.com/fusetalk
FORUMS > Performance/Modified
Topic Title: DPM? what do you think?
Created On Sat September 13, 2003 10:07 PM
Pages: [ 1 2 3 4 5 >> Next ]

NITRO WRITES:
The following is a coversation with Original Tetonice regarding DPM. I Am curios what other sleders thnk about this. Especially Mountain riders, because ICE seems to think that all mountain riders will agree with him. I want to take a poll. It is a rather long read, but might be good for a few laughs as well!!!



NITRO--------
Yes, I disconnect my DPM quite a few times. and yes, if the ignitiion wasn't in that box a well, you could throw it in your trunk. As far as the DPM manifold--- you can DEFFINITELY throw that in your trunk if you want.

DPM is identical to the old CCC-3 GM system, only it works better and is more refined. All it does is apply vaccum to the float bowl directly poportional to the decrease in density of the air--- from it baseline density. (For ski-doo this is -4*F & 0ft)

I normally ride at 800 ft ant 20 degrees. (could run 1 size leaner than baseline right??? so when I test jetting, i go closer to the edge than most, because I know that if it is to lean, I can just unplug my DPM and it will go back to baseline jetting (add a size) I Use this awesome feature for testing ALL THE TIME.

Later Ice, I hope This is helpful to you....

Original Tetonice-------------
At 800 feet that DPM isn't really functioning except for could starts where it needs to be feed fuel. And yes at sealevel you could just throw it in the trunk.

At sealevel to i believe 1000 feet the DPM doesn't function at all IMO. like it does when your riding days in the mountains will change from 6000' to 10,000' back down to 7000' and than back up again all within a 5 minute span. constantly changing fuel/air mix.

Keep in mind all my riding starts at 6000' and climbs to 10'000 try running consistant jetting, needles and pilots when your riding range is spread over 4000' in elevation?

Sat September 13, 2003 4:42 PM

NITRO-----------
Hate to tell you, but CURRENT DPM systems have no way of enriching (pressurizing the float bowl). The last sled that did that was the X and grand touring models.

Secondly, if you look at a jet chart, the temp swing for 1 main jet is about 19*F. since the baseline forall Ski-doo sleds, DPM or not, Is -4*F Yes the DPM is working at 800 ft and 20*. I can verify this by disconecting DPM and my EGTs will drop. At near 0* disconnecting it has no effect, unless at alltitude.

I beleive 2500ft is one jetsize, so actually us flatlanders benifit quite a bit since it is easy for the temp to swing from -10 to 35* in the course of a day (about 2 jet sizes)

I beleive that you may be inturpurting that dpm is actually something it isn't. DPM is nothing more than an electronic version of ATACC, THAT's ALL!!! (one exception----It is rumored that doo programed in a little less vaccum in the midrange at higher elevations to try to fix the lean midrange caused by the unhooded needle jets) 01-03 models only!

In a diff post you said that if you change jets, the DPM will "fight" the change, and thus get you no where. If this was the case, you could put a jet in 4-5 sizes leaner and the sled would run the same, right??? But it does not work that way. The sled would blow up, trust me again on this one, DPM sleds will blow up! I've done it.

The best way to prove all of this would be to install a highly accurate vaccum gauge in one of the float bowl lines. You would see that the higher you go, and warmer it gets, more vaccum is applied to the floatbowls. if you were to stop and install diff jets, the vaccum level would stay the same as it was before. The dpm has no idea how the engine is running/jetted. Only two sesors exist, 1 an air box temp sensor. 2 a brometric pressure sensor. THAT'S it!!

I have read many post's wher I have learned from you and agree with you. Just seems that on this subject you ay have gotten some bad info some where. Just trying to explain how it works as best I can.. .

Later. . . Sat September 13, 2003 8:47 PM

NITRO --------
By the way Ice. I take my DPM equiped sleds out west every year, and I have yet to touch brass. I have ridden all the way up to 11,500, and as low as 4,000 in the same day. hollow pins and lower gearing is all I do. a Quick adjust of the clickers for the alltitude and Bingo, runs the same EGT readings as at home at 800ft!

P.S. that is with mods. . .works great with mods! Sat September 13, 2003 8:52 PM


Original Tetonice---------------
Your dreaming if you think your riding at those altitude with out ever changeing your sea-level jetting. Sat September 13, 2003 9:02 PM


NITRO----------------
What do you mean?? I've done it for 3 years now..

Maybe your DPM is not working????? (any air leaks in the system and it won't work) Sat September 13, 2003 9:09 PM

NITRO ------------
What year sled did you have trouble with the DPM?? The 00's had issues with leaks, and the 01, 02 weren't a whole lot better.

In 03 they went to a smaller volume DPM manifold, it increases responsiveness, an less likely to leak. The new manifold can make changes vey fast, like droping down a 1000ft or more chute.

Are you trying to say that a Bone stock sled with DPM still requires jet changes for alltitude cahnges??? Causeif that is the case, you need to bring the sld in and have the dealer check it out, or try swapping Dpm systems with a known good sled. Sat September 13, 2003 9:13 PM


NITRO-----------
I just did some checking in my Sled library, and the first sled I ever took West with DPM was a 00 600 summit. I had about 700 miles on it in MN when I took it out west. It had 37.5 pilots and 280 mains. 309 pins were used in MN along with 23-43 gearing (757ft)

I put 308 pins in and a 21 top gear and headed west. Worked great at bear lodge in the bighorns (6000), worked great a the top of the bighorns. (10,000)

Next day worked great in cooke city (?) and up at Daisy pass. (10,000)

Next day worked great in yellowstone (5000-??)

All altitudes were checked with GPS at the time. The temp varied from -45* in yellowstone to about 20 above in the big horns. Sat September 13, 2003 9:23 PM

Original Tetonice --------------
FYI the stock 01/02 doo came stock with 500 mains for our location were my 2001 with a shaved head was running 400's and some guys were running 380's so im not sure where you come up with this blow engines notion.

You might think your sled is running real crisp when you get up in the high mountains but i can tell by your description in elevation riding that you truely haven't spent much time fine tuning in high elevation..........you ride mostly at 800 ft. come on dude.

Around here we run right on the edge lean/mean in fact from my house we depart at 6000 and therefore run not higher than 4000 to 5000 rpm not until we reach 7500' to 8000' plus do we dare run WFO.

And furthermore you seem to think your DPM works like it was designed to do down at 800 ft. so im not even sure you really know what the DPM does when the DPM is in its real element which is high mountain not sealevel or just above.

The DPM fuel managment system is an enrichment system which is always mixing the fuel/air mix at elevations. It's very noticeable when the motor has cooled since the system calculates that the engine temp/ air atmospher is down or cold like earl mornings and the system will enrich itself just to maintain idle

If your sled is setup correctly 1st starts on a cold morning should take no more than 3 pulls at half choke and than with choke off and no throttle to assist at 6000' the system calibrates the elevation (remember you just turned it on)

There's a few thing that indicate yuou not really a tuner and i don't mean tis to be negative but your statemant ofrunning 4 to 5 steps lean will cause you to blow up is BS. were down 10 to 12 steps like i pointed out above.

And to think the DPM fuel system is nothing but an enrichment system is a a little off the wall as well.

Im not trying to rude and i go through this argument with alot of sea-level guys who at sealevel don't evn get the benefit off the system. So my conclusion would be to head my way next time your out west and show you 1st hand how the fuel system really works. Sat September 13, 2003 9:30 PM


NITRO---------------
I ran an 01 too. 500 mains here and out west, exact same EGT READINGS AT WOT in both places.

I have given up on convincing you. DPM DOES NOT ENRICH A SLED, IT LEANS IT OUT!!!! You must have read that old race manual article (written in 98 and they haven;t changed it)

LATER...... I will agree to dissagree for now. Sat September 13, 2003 9:39 PM


Original Tetonice ----------------
I run into alot of folks from MN who think there Doos run great, so they think and im not saying that to be rude.

FYI I've never run the 600 they don't turn the track speed in my backyard. But I have lots of mountain time with the HAC 670 clear through the DPM 700/800's.

And believe me the system from a mountain riding stand point is nothing more than a enrichment system that can also lean out the air fuel mix by calculating the air atmospher and engine temp.

Thats really what the system is my friend in basic simple english terms. And like i said not to be rude just explaining it plain and simple.

Sat September 13, 2003 9:40 PM

NITRO -------------
P.S. the DPM does not use engine temp, verify this by disconnecting the temp sensor. It is just used for the idiot lite. . .how do I know?? I have a Digitron with the WT sensor, so no stock sensor!! still works great....

Sat September 13, 2003 9:42 PM

Original Tetonice ------------
Do you think theres a temp display that comes stock with your sled ? Sat September 13, 2003 9:44 PM

NITRO------------
Idiotlite, yes! Sat September 13, 2003 9:46 PM

NITRO----------
Sorry that you are so confused.

You run so lean beause you ARE NOT RUNNING DPM! I don't need to do that becuse The DPM does it for ME!!

I have talked at length to doo engineers about this, and My data is correct. Sat September 13, 2003 9:45 PM

idooski
09-16-2003, 03:44 PM
I was in on some of that out there. I had to wipe the tears from my eyes from the laughter.

I believe the DPM works for temp only at a level below 2000'. According to Ice it does absolutely nothing below 3000'.

dunittoo
09-18-2003, 11:29 PM
Here's something from Ontario Snowmobiler, talking about the Rev 800HO
"As the temperature changes in relation to elevation, the DPM works similar to EFI system that instantly re-calibrates your carb and ignition timing for flawless performance"
Thats a laff, ya it flawlessly slows you down. haha

TT670
09-19-2003, 10:38 AM
I can add this: DPM DOES NOT RICHEN FUEL MIXTURE!!!!!! Its a vacuum only system designed to lower float bowl pressure. The 1999 670HO did have a air pump that provided enrichment, But that feature was dropped after that model year. TETONICE IS An A$$HOLE, as most everyone will probably agree..lol, Ive lurked on snowest and read his BS for years!!As a side note The DPM also doesnt work like the GM cc3 system either like he claims, the only similarities are they both have solenoids . The cc3 system used a mixture contol soleniod that operated on a duty cycle of 0- 10 deg of dwell angle to control fuel flow. Fuel was always present at the mc needle and the solenoid opened or closed the metering needle at a rate based on fuel requirements loaded on a preprgrammed lookup table. The DPM system never comes incontact with fuel, its simply a manifold mounted solenoid used to vary the amount of vacuum applied to the carb bowl, the vacuum source is located at the bell of the carb and its prvided via a venturi effect of intake air passing over a tube. Dont know if timing is affected during normal operation by the DPM system, However I do know the MPEM will pull timing out as engine temperature climbs higher than bombi engineers would like to see for normal operation.

Dynamo^Joe
09-19-2003, 02:52 PM
The DPM system never comes incontact with fuel, its simply a manifold mounted solenoid used to vary the amount of vacuum applied to the carb bowl, the vacuum source is located at the bell of the carb and its prvided via a venturi effect of intake air passing over a tube. Dont know if timing is affected during normal operation by the DPM system, However I do know the MPEM will pull timing out as engine temperature climbs higher than bombi engineers would like to see for normal operation.

Sounds like a fukkin catastrophe! ! ! :cussing:

Im glad ours is disconnected now. Mebbe I will get more top end, and I can't wait to try.
Will have to monitor what sled does.....

canucklehead
09-19-2003, 04:47 PM
However I do know the MPEM will pull timing out as engine temperature climbs higher than bombi engineers would like to see for normal operation.
[quote]

I would like to know how you know this to be true? Like was stated earlier in this thread, the temp sensor is only for the idiot light. What about people who don't even run the sensor?

Edit: I don't know how the quote works over here. :nervous:

dunittoo
09-19-2003, 09:49 PM
Originally posted by canucklehead@Sep 19 2003, 02:47 PM

I would like to know how you know this to be true? Like was stated earlier in this thread, the temp sensor is only for the idiot light. What about people who don't even run the sensor?



Chances are that when you unplug anything, it will default back to a safe setting.
If you're a performance rider or racer, the only way to get faster is to have it all disabled in the mpem.

TT670
09-21-2003, 12:45 AM
Originally posted by canucklehead@Sep 19 2003, 02:47 PM
However I do know the MPEM will pull timing out as engine temperature climbs higher than bombi engineers would like to see for normal operation.
[quote]

I would like to know how you know this to be true? Like was stated earlier in this thread, the temp sensor is only for the idiot light. What about people who don't even run the sensor?

Edit: I don't know how the quote works over here. :nervous:
That information including with the temperatures that timing retard began along with the increments it was retarded was read to me out of a ski doo manual over the phone last spring.. Cant remember the numbers but the timing retard occurred before the temp light came on.

PANTERAONE
09-29-2003, 11:00 PM
i removed my dpm last year,didnt notice any difference,i added heated carbs(did not come on the 01's)and found it was too cluttered,so the dpm came off..all my riding is at 700-800 above sea level with lots of -20 to -35 c...

TT670
10-05-2003, 12:12 AM
I also need to add on the timing issue, on the 2003 REV the sensor has 4 wires, 2 run to the instrument cluster the other 2 plug into the mpem.

hillpounder
10-05-2003, 02:32 AM
thanks TT, was wondering about that. Have you ever noticed a drop of rpms due to temp activated retard? Rmk's I've ridden do it often, jump off the road into the powder and all is well again, it's a pita when your climbing though. Some guys fool it with a resistor, wondered how sensitive the doo is?

TT670
10-05-2003, 12:32 PM
I didnt learn that timing was temp sensitive till late last season so I havent paid much attention, I will this yr. I was also thinking about fooling the computer, I think it would be as simple as removing the sensor and tying the thing, wires and all out of the way with a zip tie, then it will read ambient temp. If you wanted to retain the temp light you could just use the old style sensor for that function. I agree the techy way would be to measur the resistance of a cold sensor and solder in the right resistor and be done.. maybe Ill try that. I was also thinking about one of Powderlites rear tunnel extension kits, they come with new running board coolers and a rear cooler too. Ive got an expert x skid going in and I have no clue if I can use or even want to use the 03 beavertail. Ive I need to extend the tunnel it will be with a powderlite kit, then Ill have no worries.

hillpounder
10-05-2003, 10:11 PM
TT, just some thoughts, when you put the expertX in you'll lose the tunnel support the stock rear skid mounts provided. So keep that in mind with your plan to remove the beaver, maybe design some additional running board/tunnel support too.