I am hoping I can find an answer to a heating issue I have been trying to solve for quite some time. My build for my 911 LS1 is at:

http://forums.pelicanparts.com/porsc...ersion-16.html

I have an LS1 stock crate long block motor from GM from an 04 Corvette. I used the intakes from my older 02 LS1 and other parts/computer, etc on the motor. It is running great except a heating issue! I swapped out my rear radiator made by Ron Davis Radiators which was a single pass radiator with two 14" Spal fans for a slightly larger triple pass radiator with a single 16" Spal fan. MY RADIATOR IS NOT IN THE FRONT. IT IS IN THE REAR ABOVE THE ENGINE. IT IS WELL BLED AND NO AIR EXISTS IN IT. IT SITS WHERE A 930 TURBO INTERCOOLER WOULD SIT AND OPENS AND SWINGS UP WITH THE ENGINE HOOD. I basically have the same issues I had with the other radiator now with this setup. The car run cool until I hit about 4000 rpms and then the temps climb. My fan is set to kick on at 195 and shuts back off when it reaches 185. It goes back and forth all day that way. But... When I ride the card to 3500 or 4000 rpms the temp climbs. I just put the car into second gear and drove about 4 miles and the car went to about 225. It would have gone higher if I kept at that engine speed. The same thing happens in 5th gear at higher speeds but with the same rpms.

Am I missing something? I realize that the only solution may be a larger radiator and I know that guys with their radiators in the front are having no issues. The new 911's have front mounted radiators. The air cooled ones like mine had no radiators so I could have put mine in the front and cut up the car but I chose to be a little different and put it in the rear. Could something be causing the higher temps at higher rpm's other then the radiator not being large enough? These radiators are really meant for any setup I thought. I have a 50 GPM electric water pump. I had a 55GPM one but swapped it out thinking I was pushing the coolant through too quickly. I tried with and without the thermostat. Currently the thermostat is inline where the coolant comes out on the engine heads to go back to the radiator. I have had it on the other end also. I have attached a photo of the old radiator setup. The new one is similar.

Any help would really be appreciated!

thanks!

Yan

 

I had this same situation when I swapped in a LS4 in my Lamborghini Diablo replica. I had a sbc in it before with a electric water pump on the engine and another inline electric water pump between my rear mounted radiators (I have dual rads). It never got hot, ever....

When I swapped in the LS4 I only used the fatory belt driven LS4 water pump and it cooled good in the winter months but when summer got here it would hit higher temps when I keep the RPM's up for more than a few minutes. I put back in the inline electric water pump and the cooling has been fine ever since even on 100+ degree summer days.

But Im not saying this will fix your problem, it worked on mine I think because I have 2 radaitors run in a series. I do have decent air flow, it sounds like you just dont have good air flow. You might look into getting a electric inline water pump, just put a relay on it with its own power souce and wire it into your electric fans so it comes own with them.

You might also look to see if there is a way you can put in some air deflectors or something. You gotta get the air not only going thru the radaitor, but flowing out and away also.....

 

tonypaul, I have an electric water pump. Same as an inline electric water pump? My pump is always on. One must circulate the coolant. The fan is controlled by the ecu and goes on and off as previously prescribed. I have a couple questions for you:

1: what temp do your fans go on and what temp do they go off?
2: are your two radiators that you run in series a single pass/duel pass or triple pass? and what are there sizes? What size fans and how many do you have? How many GPM on your water pump?

It could be that in normal operating modes with a fan in the front I would have no problem at all but since mine are in the rear I don't get the flow and rely on the electric fans to pull in the air. Perhaps it is just size...

thanks!

 

Here is the new setup with the radiator peering through the over sized whale tail:

 

And here is the fan peeking throught the rear of the tail:

 

From the pics it looks like maybe your just not getting the air out. It looks like your getting enough in but maybe not out.... Just a guess though...

1: Right now my fans are wired to come on with key on. I had one of those electric fan temp switch thingys with a dial to adjust the on/off but it stopped working~
2: My rads are custom made triple pass from Griffen, their pretty small about 17"x11". I have 1 Spal fan on each rad as a puller not sure of the size of the fans but they fit within the outter tanks of the rads. I still have the factory LS4 belt driven water pump and 1 electric inline water pump between the rads. This is the inline electric water pump Im using: http://www.ebay.com/itm/Brand-New-PR...-/360375857101 But I got it at Summit Racing about 3 years ago.

I wish I could offer you some more info, have you tried contacting http://renegadehybrids.com/ or any other people who have done the LS/Porsche swaps for advice?

EDIT: Just read some of your build thread (great build btw) so Im guessing you have been in contact with Renegade....

2nd edit- BTW do you have a A/F gauge in your car? Just wondering what your A/F readings are in the 4k rpm area......

 

tonypaul, thanks for the info. It really helped. I got my kit from Renegade and they are awesome. Even though I am not following their front mounted radiator design they always give great advise. I will assume that your fans are probably 11" fans and nothing beats spal fans. They can pull like no other - high amps! Do you have a photo of your fans and setup? I guess your duel fans are a little smaller then my single fan as far as square inches go. Do you have digital gauges or a computer to monitor your coolant temp? I have an Elm327 device with my iphone/wifi and use Rev2 from app store. It gives me coolant temp and rpm very accurately. Have you ever measure your temps at say - 4000 rpm for 5 miles. That is the only time I have trouble. Tonight I did it in second gear at 4000 and it got above 220 after about 4 or so miles. The only reason I worry about it is that at 70 MPH in 5th gear my G50 tranny revs at 3000 rpm's and if I go a little faster on a hot day my temp shoot right up. It limits long trips at higher speeds. I was also hoping that someone might chime in come up with something I have not even thought of. Not sure why at about 4000 the temps just jump right up. Slowing and lowering the Rpms cools the system right down.

thanks again!

 

I just read your entire build thread.... Great read! Its clear that you got something going on with the cooling seeing that its doing basicly the same thing with 2 different setups.

At this point- the first thing I would do is have your tune checked or atleast monitor your A/F very closely. It might be somthing as simple as your motor going lean at higher rpm and causing excess heat.

Did you have the new motor retuned after the first one failed? What did you do with the steam port lines? Did you block them off or did you vent it into your cooling system?

Im really starting to think that your problem isnt related to the radiator/fan/ect but something else..... Also how many amps is your alternator putting out at higher rpm's? What fuel pump are you running and how is it wired?

To answer some of your questions- I have VDO mech gauges and since Im running Microsquirt to run my motor I have a laptop in the car with Tunerstudio that has everything displayed.

 

This the only pic I can find on this computer that shows the rear of the car. The two black grilles behid the bumper is where my rads are mounted. The other pic kinda from the top shows where the air is pulled into.

Unlike your setup I dont have as much of a air flow problem as you, but it still takes more effort to cool than a front mounted radator setup....

 

Engine timing can affect heat output. Make sure it is sufficiently advanced.

Having said that I will bet a dollar your problems are air flow related. With a front mounted radiator the fans won't be on when the car is moving. You have challenges in that regard. A bigger radiator might help, but until you address the air flow it is the wrong fix.

Do you have those fans set up to blow up or suck down? You might have some turbulence issue over the rear deck when moving. Can you try running with the whale tail removed and see if that helps? I've seen other threads where guys had to do things like cut holes in wheel wells to get more air movement through the engine bay.

I hate to say it but I can't count the number of threads I have read with the words "overheating" and "spal" in it. Drawing a lot of current doesn't mean it moves a lot of air. Not hating on them, just telling you what I read. Often times the solution is replacing the spal stuff with a OEM fan.

Tough problem. When I first saw the title with "911" and "cooling issues" I thought yup, not the first time I've seen a thread about that.

 

Pop N Wood, I realize that I am going to have some issues with pulling the air through. Most fans companies give you CFM that they pull. I've tried some and wondered why they can't pull the air through. They work great when you plug them in on your garage floor but up against the radiator they don't work so well. They don't let you know what amps they draw. The spal fans do and there is a huge increase in pulling ability with them. That being said - OEM fans are also amazing and usually have a huge draw on amps - They work just as good but are for specific cars and radiators usually. They don't make an OEM one for my setup. Tonypaul's setup has a rear radiator design and he says his works. I believe his radiators are vented at the rear bumper. Not sure yet if they suck into the engine compartment or have their own tunnels. Mine pull air from the whale tail above it downward into the engine bay and out the rear of the car. I think quite a bit gets into the engine bay. I can drive all day long and never overheat until I reach about 4000 rpms. Even if I am going slow like in second gear at 4000 rpm it still happens. I see your turbulence issue if I was going 150 mph and perhaps air was just not able to be pulled through but it happens when I go 4000 rpm in any gear.

 

Tonypaul, do you know what numbers I should have with A/F? Do they change at different rpms? I took a picture of where my steam tube goes back into the cooling system. It re-enters right behind the electric water pump where it is sucked back in. There is just one steam tub vent?

Your car is amazing. I was looking at Lambo kits - actually I still do - but hated the fact that they all seemed to have Fiero motors. Was the swap an easy swap? What tranny is used?

Are your radiators in their own tunnel? Do you have heat or ac?

 

Your problem has to be in the tune, or fuel pump, or injector(s).... My bet is the tune.

You didnt mention if you had the new motor retuned?
Your a/f will change according to rpm, but how much it changes depends on your tuner.
Your steam vents appear to be fine.

The motor swap wasnt that bad, building the Diablo was the had part. Most Lambo replica kits are crap, its more work than you can imagine..... I did "everything" myself in my garage minus the front end algimnet. It does have heat, which I dont really need in Texas. I still need to get a couple hoses made to finish up the a/c. The radiators have their own tunnel.

I just repainted the car 2 weeks ago and still havnt got it back together, still have a little more wet sanding/ buffing to do...

Get your car to a tuner!!!!!

 

I don't know much about what it takes for a rear radiator setup. but one question.. Maybe I am missing something in your thread..but do you have a heater connected or a bypass hose..

Also the T-stat is part of the routing of the water pump and heater. If you have one that in inline with the hose and not in the pump hosing . Then the Water routing may not be correct without a OEM T-Stat doing its job...??

Might try and use a OEM T-Stat ? just throwing that out there..

BC

 

Tonypaul, I never had the new motor tuned. I just used the old pcm from the 02 Camaro that fell apart on me. I was told by the guy who did the original tune that it would work fine. I listened to you and called a tuner today. I will go there this weekend. His machine is apart this week so hopefully he can give it a tune soon. My little app device for my Iphone seems to show an issue possibly according to the tuner guy. My advance timing at 4000 rpm is about 43. The tuner guy says that is high. Not sure what it means but perhaps that could be the issue. The fuel trims all looked good according to my mechanic and the tuner guy on the phone. Could that be it? One thing at a time I guess.

You have answered some really specific questions really quickly. Really appreciate it! Your radiators have a ram air type tunnel? Air flows in and is pulled in with the radiator fans and then exhaust out the back? No radiator heat hits the motor?

You have heat? Do you have a heater core up front or do you push hot air with some fans from the back? It is another thing I have to tackle here in NY. I won't have much winter driving but even a little heat helps defrost on some days. Which kit did you get that lets you put in the LS? What tranny?

thanks!!!!!!

BC - I don't have a heater hooked up yet. No tee's yet but I will one day. First things first. I don't think it is a thermostat issue...

thanks!

 

Not saying the T-Stat is the issue .but internally in the pump housing.. the T-Stat does do some internal routing of the water. Just questioning this as a possible problem, in that not using something in place of the t-stat to handle it routing of the water.

Causing some water reversion, cavitation or something where the flow at higher RPM is causing the higher temp.. ?

You might try adding the bypass hose.. Gates #18777 or do you have the heater ports plugged ?

But, like I said. I am no expert.. just throwing out thoughts in hopes of helping ya..!

BC

 

I have no heater plugs yet. My LS has a special water pump adapter so there is no routing at all. If I want heat in the future I have to add some splitters to my lines. I have checked the tstat and so far so good. Thanks for the info!

 

Try setting your fans up to push. If at a certain speed air is not making its way into into the radiator and flowing over the top in combination with your pulling fans then you would literally have no air flowing through the radiator. It only takes a couple minutes to change the push/pull configuration. Give it a try. Its free.

 

Ok.. if not using an OEM Pump. .then disregard my comments. Hope you find the issue.

(Like I said.. I most likely missed something in the beginning of the thread)..

BC

 

43 degrees of timing is VERY high. Probably going very lean...and lean runs HOT. Get that thing tuned.