Technical Torque Lim 512 - Track Limp Mode Mystery Solved

[berns]

What makes you think so? I don't think backpressure has a very strong effect on heat rejection into the coolant, + the coolant feed line into the block runs a lot closer to the turbo hotside on a bottom-mount single than it does with a stock-location TT setup...

It's all a part of the system. IATs are high from two tiny turbos working their asses off, especially in a high-rpm situation like road racing. Oil & Water are usually close by one another, impacting each other.

I'm not an engineer or thermal expert, but in my head, a larger single turbo working well within its efficiency at 15-ish psi vs two tiny turbos struggling, would bring overall temps down.

 

[DCook]

Lots of guys going single dropped temps. My oil temps dropped roughly 20-30* going single. Iat dropped significantly too being its not forcing as hot air overworking the twins. 18psi twins and 24psi single so far. Only advantage of keeping twins is them eating oil, so its self changing oil basically lol.

 

[Hydra Performance]

IAT is pretty much a function of compressor efficiency, actual pressure ratio, and intercooler effectiveness. You can't compare IATs on stock turbos huffing and puffing for dear life vs those on a nice, efficient single. You're not comparing apples to apples here.. As for Oil temps dropping with a ST, makes sense I guess seeing as the oil is going through 1x CHRA instead of two.

 

[berns]

IAT is pretty much a function of compressor efficiency, actual pressure ratio, and intercooler effectiveness. You can't compare IATs on stock turbos huffing and puffing for dear life vs those on a nice, efficient single. You're not comparing apples to apples here.. As for Oil temps dropping with a ST, makes sense I guess seeing as the oil is going through 1x CHRA instead of two.

Yes, exactly my point. Why can't we compare? I know they're different -- the case I'm trying to make is that a nice efficient single would be better for the entire system, vs two stock turbos huffing and puffing. Regardless, I'll be keeping the twins until they die, so I'm determined to make the car work.

 

[bradsm87]

You need a turbo upgrade. Stock turbos are way, way too small for sustained high RPM high boost. It'll just pump constant scorching hot air out of the compressors plus they have severely high back pressure. These two things make the engine hot in themself but also they limit your ability to run much timing advance, again pumping heaps of extra heat into the cooling system.

Good aftermarket turbos running 14psi flat to redline, lots of timing and safe AFR and you will have zero cooling issues.

 

[Jeffman]

I presume we’re talking 6MT and not 6AT. If AT then that’s another big source of heat for your cooling system.

 

[berns]

I presume we’re talking 6MT and not 6AT. If AT then that’s another big source of heat for your cooling system.

6MT. Here's a lap at Laguna Seca for the hell of it.

 

[Jeffman]

Nice.

 

[frontside0815]

You need a turbo upgrade. Stock turbos are way, way too small for sustained high RPM high boost. It'll just pump constant scorching hot air out of the compressors plus they have severely high back pressure. These two things make the engine hot in themself but also they limit your ability to run much timing advance, again pumping heaps of extra heat into the cooling system.

Good aftermarket turbos running 14psi flat to redline, lots of timing and safe AFR and you will have zero cooling issues.

Hmmm... You are right and wrong:
I run Stage 2 Turbos (TTE550) at 15-16PSI on the Track. You are right, that for example IAT is a lot cooler than with maxed out stock twins, but i still had the same Problem berns had... I never had something like that before, but the time i experienced the limited it was really hot outside...

Also i have to add, i only run 2 Oil Coolers atm (OEM and one additional) and nothing else- i will Change to a CSF Radiator in winter time and also rework the undershield for better airflow.

 

[bradsm87]

Hmmm... You are right and wrong:
I run Stage 2 Turbos (TTE550) at 15-16PSI on the Track. You are right, that for example IAT is a lot cooler than with maxed out stock twins, but i still had the same Problem berns had... I never had something like that before, but the time i experienced the limited it was really hot outside...

Also i have to add, i only run 2 Oil Coolers atm (OEM and one additional) and nothing else- i will Change to a CSF Radiator in winter time and also rework the undershield for better airflow.

Sounds like you need a track tune with a little lower boost target, a little richer AFR target and a little more timing if possible. That'll help temps.

 

[frontside0815]

Boost Target is low enough... AFR is really rich (11.0) and Timing is maxed out for the fuel i run (9°)

 

[bradsm87]

Boost Target is low enough... AFR is really rich (11.0) and Timing is maxed out for the fuel i run (9°)

Well it seems boost isn't quite low enough for track work on hot days. Going a little lower will allow more timing, both which will help temps.

U really shouldn't go richer than 11.5:1 IMO. I read something a while back demonstrating that anything richer than that has no cooling or knock suppression benefit.

 

[Rob09msport]

Wouldn't a little meth help and don't single bb turbos run an oil restrictor so in theory transfer alot less heat ?

 

[berns]

Wouldn't a little meth help and don't single bb turbos run an oil restrictor so in theory transfer alot less heat ?

Water Meth Injection could be beneficial for IATs, I'd use it only for cooling, not as supplemental fuel. It'd likely be triggered by by boost or throttle position, and would really only come into play when the car is loaded up on straights and out of turns. Not something I'd love to do because it adds one more thing to break, more weight, worrying about fluid level, etc... But not a bad idea.

The oil restrictor needed for a CHRA doesn't have much to do with heat, it's just to restrict the amount of oil going into the CHRA so it doesn't blow the seals. This car will eventually get a single turbo, it's just not my main priority right now while I'm still sorting out the chassis and have to widen out the rear fenders so I can run a square wheel setup around 18x10 +25. Sunroof still hasto come out too, and then it's time for aero. Once that's all done, I'll be ready to go single.

 

[Rob09msport]

Water Meth Injection could be beneficial for IATs, I'd use it only for cooling, not as supplemental fuel. It'd likely be triggered by by boost or throttle position, and would really only come into play when the car is loaded up on straights and out of turns. Not something I'd love to do because it adds one more thing to break, more weight, worrying about fluid level, etc... But not a bad idea.

The oil restrictor needed for a CHRA doesn't have much to do with heat, it's just to restrict the amount of oil going into the CHRA so it doesn't blow the seals. This car will eventually get a single turbo, it's just not my main priority right now while I'm still sorting out the chassis and have to widen out the rear fenders so I can run a square wheel setup around 18x10 +25. Sunroof still hasto come out too, and then it's time for aero. Once that's all done, I'll be ready to go single.

I understand that it's purpose isn't heat but a by product of volume reduction will be reduction in heat transfer because technically their is less surface area "oil" . In cooling circuit the two largest factors are surface area and flow as long as the coolant "oil" is reaching its thermal capacity then flow has direct relationship with how much heat gets transferred

 

[kayzrx82]

I think the reason some singles are seeing coolant temps drop is that they aren't using a water cooled turbo which is adding heat to the coolant system. You will still have a problem with coolant temps on a single during sustained use (tracking) regardless of the turbo setup or turbo efficiency on the stock cooling system.

If you were running stock boost pressures then yes you would reduce the cooling load on the cooling system, but that's usually never the case when choosing a single. As long as boost is increased, cylinder pressures go up increasing the amount of heat rejected into the cooling system. The stock cooling system is too small to handle the added heat from the increased cylinder pressures during sustained use. You can get away with a small cooling system doing occasional pulls here and there or even dragging the car but track use will definitely bring up the limits of your cooling system.

Keep in mind adding a single usually involves adding a larger inter-cooler. This will help iat but you will limiting the amount of heat that can be rejected by the radiator. This is due to the reduced amount of air that gets to the radiator and also the increased temperature of the air that reached the radiator because it was heated by the inter-cooler. Cowling , larger air intakes on the front of the car, a decent auxiliary cooler and or rear mounted radiators are ways to address cooling on a track car. Keep in mind the higher the cooling temps, the smaller the radiator that is needed to reject a set amount of heat. If you are targeting a lower coolant temperature will need more surface area to reject that amount of heat. There are a lot of variables at play here that need to be considered as a whole to address cooling for track conditions.

 

[I am Jacks N54]

@berns Do you still have A/C? I assume so, because Los Angeles.

I'll be following along intently. Thanks for openly sharing.

 

[Rob09msport]

I think the reason some singles are seeing coolant temps drop is that they aren't using a water cooled turbo which is adding heat to the coolant system. You will still have a problem with coolant temps on a single during sustained use (tracking) regardless of the turbo setup or turbo efficiency on the stock cooling system.

If you were running stock boost pressures then yes you would reduce the cooling load on the cooling system, but that's usually never the case when choosing a single. As long as boost is increased, cylinder pressures go up increasing the amount of heat rejected into the cooling system. The stock cooling system is too small to handle the added heat from the increased cylinder pressures during sustained use. You can get away with a small cooling system doing occasional pulls here and there or even dragging the car but track use will definitely bring up the limits of your cooling system.

Keep in mind adding a single usually involves adding a larger inter-cooler. This will help iat but you will limiting the amount of heat that can be rejected by the radiator. This is due to the reduced amount of air that gets to the radiator and also the increased temperature of the air that reached the radiator because it was heated by the inter-cooler. Cowling , larger air intakes on the front of the car, a decent auxiliary cooler and or rear mounted radiators are ways to address cooling on a track car. Keep in mind the higher the cooling temps, the smaller the radiator that is needed to reject a set amount of heat. If you are targeting a lower coolant temperature will need more surface area to reject that amount of heat. There are a lot of variables at play here that need to be considered as a whole to address cooling for track conditions.

Excellent point which brings a question would it be more beneficial to run an aux wheel well cooler before or after main radiator. I always thought after cause it has cooler air but you made valid point .

 

[MDORPHN]

FWIW, I've retained the stock auxiliary radiator and 850W (?) fan on my 1M.

I'm running a Mishimoto radiator and regret not going with the CSF which may be just a bit more efficient.

I have a very large, custom-built intercooler fabricated by Bobby Downes (Overrev Fabrication/MOTIV Motorsport) and we're just beginning to collect temp readings inside the engine compartment and other temp-related data to help us better assess the trade-offs, including between IATs and coolant temps. We may experiment with a smaller intercooler to get more airflow through the radiator.

I've considered getting rid of the AC to increase airflow through the radiator, but decided to retain it until my 1M is a pure track car and I'm no longer running the One Lap of America in it.

Neil

 

[fmorelli]

@berns you should ask Jake H what all was done on the Motiv 1M track car, that thing never has any cooling issues as far as I know.

Curious how much sprint totenduro o tra time that car has seen (i.e. more than 3 hot laps at a time)? Would be good info.

Filippo