LOST JEEPS :: View topic - Cruse control when towing up hill may be a turbo killer

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Cruse control when towing up hill may be a turbo killer http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=44244	Page 1 of 1

Author:	warp2diesel [ Tue Jun 16, 2009 5:31 pm ]
Post subject:	Cruse control when towing up hill may be a turbo killer
When I was trailer towing this past week end, I went up a steep river bluff (like a micro mini Lovland pass) and used the cruse control. Part way up the hill the transmission down shifted and the tach climbed to 3500, boost went up toward 20 PSI, EGT over 1250F, back pressure with stock exhaust system was 4.5 PSI, at 80f ambiant. When I headed home with a load in the trailer and the CRD laded down as well, I passed up a slow truck with the accelerator floored, the tach climbed to 3500, boost up to 20 PSI, EGT climbed to 1400 F before my size 13 lifted up a tad dropping it back to 1200F, and the back pressure went up to 5 PSI at 80F ambiant. What I suspect is that the high revs with a load and the stock exhaust, the EGT will shoot up to the danger point. Had I not had the gauges, I would have never known I had a potential problem and I could have damaged my turbo. For the rest of the trip, I only used cruse when I was on the flat lands and not when bluff climbing. I hope my straight through Magnaflow will lower the EGT along with the Back pressure.

Author:	geordi [ Tue Jun 16, 2009 5:53 pm ]
Post subject:
Hmm, good to know. I've got a Flowmaster on mine, and no kitty anymore, so the back pressure shouldn't be an issue anymore. Of course I've only driven 10 miles with the EGT installed, and then the #1 piston decided to end it's employment. I haven't driven it since, and that was 4 months ago.

Author:	Glend [ Tue Jun 16, 2009 7:47 pm ]
Post subject:
It is just good practice to stay out of overdrive and cruise control on steep sections when towing. Cruise control will provoke a downshift to third gear (thus your high revs and associated EGT levels). Cruise control will also downshift going down hill when you overrun the set speed by a certain amount and off throttle compression affect cannot slow the vehicle (I've had this happen to me once and it was scary, especially with a laden trailer on the back). The KJ CRD is a great little vehicle with good towing capability but we all have to accept that sometimes we cannot hold the speed limit in all situations, so operating out of overdrive and just taking it easier is IMHO the best approach.

Author:	gmctd [ Tue Jun 16, 2009 7:57 pm ]
Post subject:
Good report, and you done good to back it off, considering - however, that level of EBP is nothing to worry about at 20psi Boost - compressing air does require power - even the EGT's are not too bad, long as you don't hang there for a length of time - it's when EBP approaches Boost that you gotta worry about the turbine blades deforming at high EGT levels - not having more empirical data on towing conditions with this chassis, we don't have established fact for upper limits of EGT vs duration at any temp - 1250F may be safe for long periods, long as IAT is not up ~300F - CATCRD just did some tests indicating that IAT is safely managed, but with the ac on at those levels, who knows - you cannot cool 250* air with 250* air, regardless of flowrate and volume across the heat exchanger, no matter how high it's efficiency specs..................... http://www.lostjeeps.com/forum/phpBB3/vie ... hp?t=44175

Author:	warp2diesel [ Tue Jun 16, 2009 8:29 pm ]
Post subject:	I don't take it out of OD
Glend wrote: It is just good practice to stay out of overdrive and cruise control on steep sections when towing. Cruise control will provoke a downshift to third gear (thus your high revs and associated EGT levels). Cruise control will also downshift going down hill when you overrun the set speed by a certain amount and off throttle compression affect cannot slow the vehicle (I've had this happen to me once and it was scary, especially with a laden trailer on the back). The KJ CRD is a great little vehicle with good towing capability but we all have to accept that sometimes we cannot hold the speed limit in all situations, so operating out of overdrive and just taking it easier is IMHO the best approach. I watch my gauges and use my foot to control the shifting. Going up the bluffs with the trailer it down shifted into 4th and did fine. I had no problems on the slight corn belt prairie grades pulling the trailer in OD. With a trailer that has a large frontal area, dropping out of OD may be needed. With the U-Haul cargo trailer I rented or my flat bed beaver tail the frontal area is not that large and staying in OD works. Either way no more cruse control when pulling a trailer up or down a bluff or steep hill.

Author:	grywlfbg [ Tue Jun 16, 2009 9:25 pm ]
Post subject:
Yeah, if the CRD can't hold 55mph in 5th I'll hit the OD button so it'll lock up again in 4th. I hate how cruise will force it to kick down all the way to 3rd.

Author:	CATCRD [ Tue Jun 16, 2009 9:41 pm ]
Post subject:
grywlfbg wrote: Yeah, if the CRD can't hold 55mph in 5th I'll hit the OD button so it'll lock up again in 4th. I hate how cruise will force it to kick down all the way to 3rd. Hitting the o/d off button kicks it down to third with lockup.

Author:	yakers [ Tue Jun 16, 2009 10:35 pm ]
Post subject:
Well there is no way I want or could use cruise or OD going up steep grades especially towing. But I want to max the CRD especially the trans life, so when I get to serious grades like the Grapevine and mountains around Tahoe I switch off OD and it seem to climb well. If I see the temp gauge go up a bit I make sure the AC goes off if it had been on. On the flats of US 5 across C I do tow in 4th @60MPH indicated. Seems to work well. The travel trailer varies from 2,500 to 3,500 lbs but does push a little wind so I don't go over 60 even though it often feels it can. Is there anything else I should be doing? An ideal vehicle or engine speed for climbing?

Author:	Glend [ Wed Jun 17, 2009 2:11 am ]
Post subject:
I just try to stay in the peak part of the torque band (1800 - 2500 rpm) when climbing, with whatever gear will keep me there. Obviously the lower down in the peak torque band you can sit the more economical the trip will be.

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