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  #31  
Old 08-24-2013, 06:52 PM
v8volvo v8volvo is offline
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tomorrow morning I'll be shooting for 4000rpm in 1st gear with light throttle if I can manage it safely traffic wise, although I probably have enough power and cooling to do the climb in 2nd.
1st gear is pretty short. I'll wager you will do OK in 2nd or perhaps even 3rd on flatter stretches depending on how it seems to do and how warm it is outside. I don't know whether going up to really high sustained engine speeds will help or be detrimental. I think the reason somewhat elevated revs help is that you can keep the car moving while keeping the load on the motor light, and simultaneously spinning the water pump and fan at a good rate of speed -- I think you achieve those things satisfactorily by about 3000 rpm. Going further beyond that I think the goal is vehicle speed more than cooling effect, assuming you can do it without making boost and EGT rise significantly. My non-scientific sense is that around 3300-3500 is a good spot, or at least that seems to be where mine was happy; much above that, it gets difficult to keep boost down and also you're getting into an inefficient combustion range where to my mind it seems possible that heat rejection per unit of power produced might be greater than it is in the midrange. That's a conjecture, though; I'll be interested to hear your results if you try spinning it faster.

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If you see this soon enough, what are your thoughts on the altitude compensation system on the injector pump? I'll be going high enough to trigger it, and it's operational still. If advanced timing with a hot engine is a problem should I bypass it? My timing is set to the factory 0.85mm.
Dunno, I generally run mine with the wires jumpered at the barometric switch to keep the system from engaging, but I also run more static timing than you do (~0.95mm). I don't think we have a way of quantifying how much advance that system adds in terms of mm of plunger travel at TDC; however, I got to be present while a D24T VE pump was being run on a calibration bench recently and watch the various timing advance mechanisms in action, and we concluded that the altitude compensation solenoid adds about a degree at low rpm and a degree and a half in the upper end. Hard to reach any concrete conclusions without seeing a lot of engineering data about how combustion temps and actual start of ignition are affected in this engine by the combined factors of altitude, ambient temp, engine temp, and start-of-injection timing, but my tentative hypothesis would be that at the timing setting you are running and the way you're planning to drive it, it won't make much difference whether it's engaged or not. In high-load situations where the duration of the injection events is relatively long, insufficient timing advance can significantly increase EGT, so if you were going to be hammering it up the hill then you'd probably want to be sure it was connected and working, but since you're not planning to be leadfooting it that effect probably will not be a major factor. I would probably leave it connected and see what happens when you cross 3000' or wherever it kicks off -- maybe make a little jumper wire so you can disable it quickly by the roadside if you don't like what it does?

Makes us begin to appreciate the challenge that Bosch/VAG had in tuning these mechanical VE pumps to perform under varying conditions... why the TDI was such a huge step forward. Everyone that builds "m-TDIs" with mechanical pumps, I can never understand -- I guess they assume the direct injection is the main advantage they have, but I think their electronic feedback control is at least as important in making them run as well as they do.

Good luck! Objectively speaking attempting this with a 30yo car known for cooling system trouble and fragile cylinder head is nuts -- hopefully you're well aware of that -- but it sounds like you could succeed in making it work out. Let us know how it goes.

Last edited by v8volvo; 08-24-2013 at 07:08 PM.
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  #32  
Old 08-25-2013, 09:42 AM
ngoma ngoma is offline
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Originally Posted by casioqv View Post
... this is a pretty under-powered car by modern standards...
I had heard that in its day, it was the best-performing diesel passenger car. Shows how much progress has occurred.
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  #33  
Old 08-25-2013, 02:09 PM
745 TurboGreasel 745 TurboGreasel is offline
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The 524TD will give you a run for the money, but no wagon option here anyway.
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  #34  
Old 08-25-2013, 03:17 PM
Nevadan Nevadan is offline
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Here's some data from the "SAE paper 790206" - "New 5- and 6-Cylinder VW Diesel Engines for Passenger Cars and Light Duty Trucks" paper published in March 1979.

"The ratio between crankshaft and water-pump speed was raised to i = 1.1 (i = 0.85 in the gasoline engine). This results in a cooling water flow of between 140 and 170 liters per minute at rated speed, depending on the cooling-system flow resistance curve." (converts to 37 to 45 gallons per minute!)

That sounds like a lot of water moving through the engine.

My observation of the importance of a GOOD working thermostat is that when the engine is warmed up the back end of the thermostat must close the flow coming out of the block in the position right behind the thermostat, thus forcing all the fluid flow either out the back of the block or up through the water outlet on the head. The suggestion to use an 80C thermostat is probably a good idea since it opens sooner and thus closes that water flow coming out of the block.

It is probably a good idea when driving under a heavy load to turn on the heater to allow more water out the back of the head. My concern is there's not enough flow at that end of the engine, ie. in and around the head and cylinders at #'s 5 and 6. It may not make much of a difference but I like the idea!
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  #35  
Old 08-25-2013, 03:33 PM
745 TurboGreasel 745 TurboGreasel is offline
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So,me head gaskets are missing a row of 'steam holes', I wonder about adding one in the back(or more) .
Also a bypass heater valve(90s Ranger, Caprice)could give more outflow at the back, especially if you've removed the water-oil cooler.

Any idea what 'rated speed' is?
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  #36  
Old 08-25-2013, 03:45 PM
RedArrow RedArrow is offline
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Cook YOUR head instead of warping aluminium! Ask me how I know... Many, many times I saved car(s) and myself too by turning the heat on, full blast; it definitely does help a lot!
Especially because you can never really truly know how close you already got to the edge of a later serious & irreversible overheating. Yesterday I PM-d him about it and I hope he got the message in time before his departure...
Let me off-topic a little: We used to have a unique Volga wagon pimped with the 6 cyl PRV engine that was one unreliable engine, needing so many things fixed all times, and that car was slightly overheating all the time, ate a couple of headgaskets but turning the heat on always worked for years to get around town... long story from around 1978-1989. RIP, he rusted away since then, I`m sure. My Dad might be driving it in Heaven...
Heat up, open the sunroof.

Last edited by RedArrow; 08-25-2013 at 03:47 PM.
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  #37  
Old 08-25-2013, 05:03 PM
RedArrow RedArrow is offline
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Quote:
Originally Posted by 745 TurboGreasel View Post
The 524TD will give you a run for the money
Yes, the 524td was indeed a big thing those times. Although in late 70`s & early 80`s Europe already had nice diesel options with relatively reliable, low-maintenance engines. That time most of them were considered `luxury` cars... I grew up In Europe and I can tell, it was (is) something hard to get for average people... Renault, Peugeot, Audi, Bmw, Mercedes; just to name a few. My all time favourite I think stays the same for now, the d24t & the W123 MB series. Nowdays, Europe has a huge amount of diesels rocking all over the roads and almost every car manufacturer has *multiple diesel options... for example Skoda (Vw of course
This tear sheet is from a 1980 US magazine.
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  #38  
Old 08-25-2013, 08:02 PM
ngoma ngoma is offline
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Quote:
Originally Posted by Nevadan View Post
It is probably a good idea when driving under a heavy load to turn on the heater to allow more water out the back of the head.
Heater valve always open EXCEPT during max A/C. But arranging the controls for heat & max fan would maximize airflow thru the heater core, pulling more heat out of the engine and onto your feet!
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  #39  
Old 08-26-2013, 01:12 AM
745 TurboGreasel 745 TurboGreasel is offline
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Not sure if this one is the right way to 'hot' but you get the idea
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  #40  
Old 08-26-2013, 09:16 AM
casioqv casioqv is offline
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I made it no problem! I was so excited I yelled in joy when I hit the summit! Thanks for all the help and advice, I couldn't have done this without you guys. Now I get to spend a week sailing in the California Delta w/ my dad.

I climbed the grapevine at 3000-3500 rpm in 3rd gear most of the way, going down to second on the steepest bits. Peak temp was 102C when I floored it, but I could keep it under 100C. That's compared to 116C with no trailer last time I drove the same road. I think my cooling system can handle continuous full load at low speed without overheating.

After the grapevine, I was able to maintain 60mph in 4th gear, running the A/C and cruise control all the way to Sacramento and the engine stayed cool. I also never had to downshift once after getting past the grapevine. I was far from the slowest vehicle on the road. Once the weather got hot around noon power reduced a bit, and my speed dropped to 57mph.

Also, coming down the grapevine I didn't touch the brakes the whole way. With the A/C on at 3,000 rpm the D24T had enough engine braking to keep the speed constant. The brakes were cool to the touch at the bottom of the grade.
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Last edited by casioqv; 08-26-2013 at 09:20 AM.
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