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Thread: Drag Racing Engine Heats up then drops down after race.

  1. #1
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    Arrow Drag Racing Engine Heats up then drops down after race.

    Hey guys,

    In my caravan when I drag race it, the temp goes from the 180* spot on the dash at the start, and at around half track it starts moving slowly ending up at the half way point by the end of the 1/4 mile.

    The weird part is when I let off the gas the temp goes back to the 180* spot almost immediately? What could be causing this? Or is it normal?

    The van is stock other than 12psi boost and 180* thermostat.
    Last edited by jefo; 12-03-2012 at 11:20 PM.

  2. #2
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    Re: Drag Racing Engine Heats up then drops down after race.

    Turbo is heating up under long periods of WOT. Its why we use turbo timers.

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    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Drag Racing Engine Heats up then drops down after race.

    Quote Originally Posted by Tempted View Post
    Turbo is heating up under long periods of WOT. Its why we use turbo timers.
    I don't know of anyone on here using a turbo timer.

  4. #4
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    Re: Drag Racing Engine Heats up then drops down after race.

    sounds pretty normal to me... yeah its going to heat up at that boost pressure esp with out an intercooler... no need for our cars to run a turbo timer, there water cooled

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    Re: Drag Racing Engine Heats up then drops down after race.

    Quote Originally Posted by 22shelby View Post
    sounds pretty normal to me... yeah its going to heat up at that boost pressure esp with out an intercooler... no need for our cars to run a turbo timer, there water cooled
    And even if they aren't water cooled it doesn't take too long for oil temps to come back down to normal. The drive back to the pits probably takes care of that.

  6. #6
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    Detonation can shoot up temps really fast. On my van I datalogged a run that had some knock and it shot the temps over 200 pretty damn fast. Does it push coolant out of the overflow?

    Also hate to say it but a y combustion leaks into coolant can cause rising temps under throttle. I chased a overheating under boost for a long time before I tore it down and found a cracked block.
    Ian Adams Function>Form 1990 shadow scrapped, too rusty:( 1991 Spirit R/T Scrapped, parts sold:( 1989 Turbo Caravan Daily beater with built-[I]ish [/I]​engine slowly evolving into weekend turbo beater.

  7. #7
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    Re: Drag Racing Engine Heats up then drops down after race.

    It doesn't overheat, it just gets to about half way on the gauge which is the normal operating temp with the stock thermostat.

    I have never heard detonation, but I'll have to check the plugs. And no it doesn't push coolant out of the overflow.

    It doesn't seem like a big deal to me, just curious. I'm going to replace the radiator soon anyways as after long drives it starts to get warm.
    Last edited by jefo; 12-03-2012 at 11:38 PM.

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    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Drag Racing Engine Heats up then drops down after race.

    Running at WOT for 13-15 seconds will get her pretty warm if it's already at 180* especially if the rad is marginal.

  9. #9
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    Re: Drag Racing Engine Heats up then drops down after race.

    We where noticing that same thing watching many, many, cars on chassis dyno at Car Craft Summer Nationals. Guy that operates vehicle said most cars will do this. He said you can usually watch the temp gage rise and fall right with the tach. You notice stuff like this when you don't need to watch the road.
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    Last edited by 4 l-bodies; 12-06-2012 at 08:10 PM.

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    Re: Drag Racing Engine Heats up then drops down after race.

    Pretty normal especially considering our rads are too small to begin with. Do you have the fan running all the time? That helps big time.
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    Re: Drag Racing Engine Heats up then drops down after race.

    Yea I have a manual fan switch with the fan from a newer model caravan. Glad to know its normal, I'll just get a new rad and call it a day.

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    Re: Drag Racing Engine Heats up then drops down after race.

    I put the $89 radiator from Rock auto in Woody, my 89 turbo mini. It is substantially thicker than the stock unit and runs way cooler now-almost too cool at one line up with a 185 thermo

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    Re: Drag Racing Engine Heats up then drops down after race.

    My theory... and I have seen this happen....

    If the entire cooling system is not up to temp before the run, temp will spike as soon as the WOT energy builds up enough heat. And then when the thermostat opens on the run, and because it opens slowly, there is some lag allowing temp overshoot then when the t-stat opens, the temp drops rapidly, sometimes below normal.

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    Re: Drag Racing Engine Heats up then drops down after race.

    Quote Originally Posted by cordes View Post
    I don't know of anyone on here using a turbo timer.
    When I said "we" I meant turbo cars in general. I run a turbo timer ......

    But only because its part of a remote start system. Lets me warm it up from the shower on a cold morning.

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    Re: Drag Racing Engine Heats up then drops down after race.

    Can you post a link? I see 4 but they are all below $80. for the 89 dodge caravan.

    Quote Originally Posted by 2.216VTurbo View Post
    I put the $89 radiator from Rock auto in Woody, my 89 turbo mini. It is substantially thicker than the stock unit and runs way cooler now-almost too cool at one line up with a 185 thermo

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    Re: Drag Racing Engine Heats up then drops down after race.

    Quote Originally Posted by Tempted View Post
    When I said "we" I meant turbo cars in general. I run a turbo timer ......

    But only because its part of a remote start system. Lets me warm it up from the shower on a cold morning.
    Well that's one person!

  17. #17
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    Re: Drag Racing Engine Heats up then drops down after race.

    Turbo timers are for guys that want to pull up to a crowd and get out and have the car shut off, they go hand and hand with amps and subs and led head and tail lights, ebay tow hooks, stuff animals tied to the back, lighted valve stem caps, underglow lighting,aftermarket seats(other than aluminum drag seats) anything from autozone(the section you feel weird walking in) you get the picture.


    +1 on warming the engine up completely then soak before you run it hard

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    Re: Drag Racing Engine Heats up then drops down after race.

    Quote Originally Posted by 2.216VTurbo View Post
    I put the $89 radiator from Rock auto in Woody, my 89 turbo mini. It is substantially thicker than the stock unit and runs way cooler now-almost too cool at one line up with a 185 thermo
    What brand and part number?

    Quote Originally Posted by MILKCARTON View Post


    +1 on warming the engine up completely then soak before you run it hard
    Agreed, nothing like beating on a cold engine with forged pistons,
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  19. #19
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    Re: Drag Racing Engine Heats up then drops down after race.

    Quote Originally Posted by MILKCARTON View Post
    Turbo timers are for guys that want to pull up to a crowd and get out and have the car shut off, they go hand and hand with amps and subs and led head and tail lights, ebay tow hooks, stuff animals tied to the back, lighted valve stem caps, underglow lighting,aftermarket seats(other than aluminum drag seats) anything from autozone(the section you feel weird walking in) you get the picture.


    +1 on warming the engine up completely then soak before you run it hard
    No big stereo(no stereo at all actually), yellowing headlights, nice original dark red tail lights, I think I have valve stem caps??, no stuffed animal.

    Tow hooks? People put those on small turbo cars?

    Also I used my turbo timer on the 91 R/T when nobody was looking more often than in a parking lot. Felt like a douche bag when people were around. But I ran that car very hard every time I cranked it so I did all I could to keep the oil from coking. I just put remote start on the Iroc R/T and it has a timer, used it to check that it was working and not since. I fully believe in remote start, and partially believe in turbo timers. The one thing that terrifies me about either is our oil pumps. Yeah, I know its normally at higher RPMs when they fail, but having my car running without me being able to look at the vitals is un-nerving.

  20. #20
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    Re: Drag Racing Engine Heats up then drops down after race.

    I've had enough fans crap out on me that I won't run one.

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