Coolant temps spike in boost
 

I'm having an issue with what seems to be coolant temps rising rapidly during boost/hard acceleration. I recently swapped my HP coolant reroute to the FM reroute so I can run water lines for the new turbo I will be installing shortly. Current turbo is only oil cooled. Thermostat is the one supplied by FM (180f I think) I have bled the cooling system both with a vacuum bleeder and by elevating the front end of the car with a spill free funnel on the radiator. I did see some very small bubbles when it was warmed up but there were not many so I am beginning to wonder if either there is a crack in the block, a bad head gasket, or a crack in the head. Maybe the head needs a retorque? The car is an NA chassis with a 99 BP Swap. I am attaching my current tune and logs to show the rise in temps. Even at 40-50 percent throttle the temp begins to climb rapidly the once I lift off the gas the temp immediately drops back down to where it was at before the pull began. This issue seemed to occur once I swapped to a 6 speed trans for some reason though that may have been me watching ShadowDash on my head unit and seeing the issue occur. Also if anyone can look at my tune file and logs, I noticed that after an extended drive with a few on/off cycles I began to run a little lean during cruising. Target was 14.8 and was seeing 15.8-16.0

I purchased this engine from a member on here and it has been running very well so far. Here are the specs of the motor

BP4W head, stock with Supertech double heavy springs
Cometic head gasket
Built bottom:
Wiseco 83.5mm 8.5:1 cr pistons, supertech rings
ARP everything
Manley H-beam rods
Stock crank
Extra clearance bearings
Boundary Engineering oil pump

Cooling system is dual fan setup primary fan configured as normal, secondary fan still connected via AC relay as OE,
aluminum radiator (crappy ebay one but I have a spare if it comes to be the issue),
FM reroute
AC is deleted completely, no lines, no condenser. Only things that partially block the radiator would be the IC and Oil cooler

I run a reroute and see a decent temperature rise (20F) during a pull with a nearly immediate (on the order of 1-2 seconds) drop at the end of a pull as well. I have observed similar behavior on other well setup cars I have worked with. I have not been able to get confirmation on the interwebs or social networks that this is normal. That said, it makes sense to me, as I am dumping significantly more heat energy into the coolant during a pull, so I would expect the coolant exiting the motor to increase in temperature while it is sinking the additional energy, and to return to the system steady state when that heat energy source is reduced or removed.

I can also say that cars with no reroute that I have worked with do not show this same temp rise, which also makes sense to me. The heat doesn't shed as efficiently, which presents as a much smaller temperature increase (a few degrees F) but lasts much longer ( up to 30 seconds or more).

I didn't look at your logs in too much detail to compare, but I didn't see any WOT pulls which would be the easiest to look at. I do see that your fueling could really use some work. It looks like you might be running one of those FW versions that zeros EGO, and your EGO is already really weak.

Turn off fuel cut so you can get a good look at what is really happening.

Here is an example of what I would consider good fueling, "FLEX_AFRblend" is the AFR target.

https://cimg7.ibsrv.net/gimg/www.mia...5b79724393.jpg

Thanks for the input. I didn't go WOT as I was seeing the temps increase and didn't want to risk anything too crazy. Tomorrow I will get a WOT log or two and post those.

As for fueling I've driven the car maybe 100 miles since getting the swap done. I just switched from batch to sequential while doing the swap. I am concerned about the leaning out after multiple on/off drive cycles in a short period of time. You mentioned the FW version, I am not sure of the latest one or it's changes/features. It probably is due for an update.

sneak up on it and keep your eyes on that TS gauge, you don't want to pop it.

Alright went out this morning to pick up some breakfast and took a few more logs. I broke the logs down to strictly WOT pulls so it should be shorter and easier to sort through. I did a WOT second to third gear pull with temps starting around 185 and by the time I was midway through 3rd gear I saw 206 and let off. Temps went right back down to where they were before. The log WOT3 is a strictly 3rd gear pull.

I honestly can't tell you if that is normal or not. I can say that it looks similar to mine, and it also look similar to others I have worked with that were running a re-route. For reference, here is a pull on mine.

I have at times been convinced that it was head lift, but I am now in the camp that this is expected. I would love to see some actual screen shots from others showing the same or otherwise.

One interesting observation about the shot posted below, the hump you see in the middle of the pull correlates pretty closely with where I transition from twin-charged to fully turbo. Back when I had EGP sensors, this is where the manifold pressure (and temperature) starts spiking. This is a water cooled turbo. I wonder if this is what FM is mitigating with their new re-route that runs the turbo coolant through the radiator. I do plan on plumbing my setup that way over the winter.

https://cimg9.ibsrv.net/gimg/www.mia...812448c4b2.png

I know this thread is old, but Im having the exact same issue on my car. I saw +45F coolant temp increase (210 to 255!) with a 3rd gear pull. Was driving uphill and it was 95F out. Coolant temp went back to 210F with a couple seconds after letting off. The water temp gauge in the dash doesnt react fast enough to show it.

It drives fine with no issues. No coolant in oil, no oil in coolant, radiator and expansion tank are full, no signs of detonation on spark plugs. The temp sensor is on the back of the head, maybe I need to install a reroute. Im kinda spooked by the 255F temp...

https://cimg8.ibsrv.net/gimg/www.mia...1ece610b0c.png


I checked my old logs from last year. It didnt go as high with a similar pull, but this was on a flat road and it was a little cooler out.
https://cimg4.ibsrv.net/gimg/www.mia...bd6e43249c.png

Standard beginning Miata turbo issues.

Consider adding an oil temp sensor somewhere. One with an alarm is nice (Prosport makes one).

If your airflow to the radiator is impeded by the intercooler you are doing it wrong. Radiator has primacy. Intercooler is significantly less important.

Why wouldn't you run a reroute?

Why would you ask about cooling without details like what radiator you have? Fan(s)? Year model? Ducting? All make a difference.

I am running a reroute. Just added LRB skid tray. I'm running a TSE triple pass radiator, oem fan, and switched to a FM Intercooler instead of the longer crapo eBay one I had been running for years. I still get a spike but it isn't as bad. It only shows in data but not on the gauge. No loss in coolant. I wonder if it's just a quick heat soak issue of the sensor itself. Maybe a weak water pump.

EDIT: I thought you were asking me. I saw another person commented with the same issue. But this is what I'm running and still have the concern but not as bad

It has a 52mm ebay alum radiator, oem fan, oem ducting with intercooler hose holes sealed, room for air to go around intercooler, 60/40 water to antifreeze with water wetter, and no reroute.

The sensor thats seeing the spike is on the back of the head right where the coolant come outs of the engine. It hasnt gone through the radiator or had time to cool yet. So the temp spike is from the coolant taking a lot more heat out of the engine in boost.

I'm actually thinking there might be something wrong with my temp sensor or a flakey connection. It no longer matches my other coolant gauge with a sensor in the same spot.