does heatsoak limit boost?
#1
does heatsoak limit boost?
My car is running at 12-15psi depending on the gear. After a couple of hot laps, it seems limited to 8psi. Is this because of heat soak? They are BNR S3 twin turbos with a stock mount intercooler.
My water temps stayed under 78 degrees the entire time as well, usually between 73-75C.
My water temps stayed under 78 degrees the entire time as well, usually between 73-75C.
Last edited by mkiv98; 04-14-18 at 01:49 PM.
#2
RX-7 Bad Ass
iTrader: (55)
Jesus, that much boost on BNR's on a stock IC? I think you need an IC!
The PowerFC, for example, will retard timing when intake air temps climb. I'm assuming you're running something like that. Your intake air temps are probably through the roof. Retarding timing will decrease power quite a bit. I'm not sure if something will dial boost back, but it's probably good that boost is dialing back.
If you're stuck with the stock IC (I see you're in Cali and I know a lot of Cali guys have to do what they can due to CARB and whatnot) you may want to improve ducting to it and look at adding water injection to help intake air temps.
Dale
The PowerFC, for example, will retard timing when intake air temps climb. I'm assuming you're running something like that. Your intake air temps are probably through the roof. Retarding timing will decrease power quite a bit. I'm not sure if something will dial boost back, but it's probably good that boost is dialing back.
If you're stuck with the stock IC (I see you're in Cali and I know a lot of Cali guys have to do what they can due to CARB and whatnot) you may want to improve ducting to it and look at adding water injection to help intake air temps.
Dale
#3
Racecar - Formula 2000
Is it an OEM IC, or an aftermarket SMIC? That seems not clear from the description.
#4
Jesus, that much boost on BNR's on a stock IC? I think you need an IC!
The PowerFC, for example, will retard timing when intake air temps climb. I'm assuming you're running something like that. Your intake air temps are probably through the roof. Retarding timing will decrease power quite a bit. I'm not sure if something will dial boost back, but it's probably good that boost is dialing back.
If you're stuck with the stock IC (I see you're in Cali and I know a lot of Cali guys have to do what they can due to CARB and whatnot) you may want to improve ducting to it and look at adding water injection to help intake air temps.
Dale
The PowerFC, for example, will retard timing when intake air temps climb. I'm assuming you're running something like that. Your intake air temps are probably through the roof. Retarding timing will decrease power quite a bit. I'm not sure if something will dial boost back, but it's probably good that boost is dialing back.
If you're stuck with the stock IC (I see you're in Cali and I know a lot of Cali guys have to do what they can due to CARB and whatnot) you may want to improve ducting to it and look at adding water injection to help intake air temps.
Dale
I just went around and measured my IATs, my gauge says around 63C driving around, and after parking for a while it went up to 80C!
The next step for me is a vmount, but I have another track day coming up. Would it be safe for the engine to run the car again with these IATs and just take it easy on boost? I am using an adaptronic select ECU.
#5
RX-7 Bad Ass
iTrader: (55)
Wow, that is pretty hot! I typically see intake air temps in the 40's with my front mount. You may be able to get the temps better with good ducting.
Also a fast acting intake air temp sensor can help.
Dale
Also a fast acting intake air temp sensor can help.
Dale
#7
RX-7 Bad Ass
iTrader: (55)
Not sure who all is carrying the fast air temp sensor kits currently, just Google around. Best is moving it but just using the stock location is 80% of the benefit IMHO.
Dale
Dale
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#8
Urban Combat Vet
iTrader: (16)
Fast reacting sensor—-> Fast Reacting Sensors - Wannaspeed
As DC said, just moving it from under the UIM will be significant. I moved it to just downstream of the IC outlet. It’s really pretty easy to do. Hardest part was reaching under and unpluging the stock IAT sensor which you just leave in place. Then and solder an extension for the harness so it will reach where you need to go and buy a new stock or fast reacting sensor to install. If you get the fast sensor I recommend his p n p harness too.
As DC said, just moving it from under the UIM will be significant. I moved it to just downstream of the IC outlet. It’s really pretty easy to do. Hardest part was reaching under and unpluging the stock IAT sensor which you just leave in place. Then and solder an extension for the harness so it will reach where you need to go and buy a new stock or fast reacting sensor to install. If you get the fast sensor I recommend his p n p harness too.
#10
TANSTAFL
iTrader: (13)
One thing that can happen as things heat up is a collapsing inlet duct. Common fix is replaced compressor inlets with wire reinforced ducting from mcmaster.
You can do a cheapo air intake temp sensor kit yourself. Get a Triumph motorcycle intake temp sensor and a Bosch injector connector from an old Volvo at the junkyard. The sensor has a similar ohm/temp curve as the oem. Put it in the TB elbow or IC outlet. Or buy the kit.
I'm gonna guess you have inadequate ducting on your IC. In that case you could get those temps down without spending much money. Do you still have the intake/battery/AC dryer stealing air from the IC duct? That and the recessed inlet of the duct are the main weak points.
For comparison I've got stock twins running 11 psi and I don't see 60C unless I leave the hood closed at an autocross in between runs in grid. Typical around town temp is 40/45C. Modified the ducting on mine. Stock Mazda intercooler.
You can do a cheapo air intake temp sensor kit yourself. Get a Triumph motorcycle intake temp sensor and a Bosch injector connector from an old Volvo at the junkyard. The sensor has a similar ohm/temp curve as the oem. Put it in the TB elbow or IC outlet. Or buy the kit.
I'm gonna guess you have inadequate ducting on your IC. In that case you could get those temps down without spending much money. Do you still have the intake/battery/AC dryer stealing air from the IC duct? That and the recessed inlet of the duct are the main weak points.
For comparison I've got stock twins running 11 psi and I don't see 60C unless I leave the hood closed at an autocross in between runs in grid. Typical around town temp is 40/45C. Modified the ducting on mine. Stock Mazda intercooler.
#12
Urban Combat Vet
iTrader: (16)
Yes. Immediately plug that hole to the old battery tray and the hole that used to lead to the stock intake box. All the air that leaks out there should be going thru the face of your IC. Hard to tell, but it doesn't look like the entire face of the IC is covered by the duct.
#13
Yes. Immediately plug that hole to the old battery tray and the hole that used to lead to the stock intake box. All the air that leaks out there should be going thru the face of your IC. Hard to tell, but it doesn't look like the entire face of the IC is covered by the duct.
#15
TANSTAFL
iTrader: (13)
Think of it like this. You want to force as much air over the intercooler as possible. So, you pressurize the inlet and make sure every ounce of air goes over those fins.
To pressurize the inlet you can extend the ducting into the bumper opening with some aluminum. The stock duct is incapable scavenging air from the bumper opening.
Here's a link to my thread with pictures of my ducting if you're looking for something to reference. I used aluminum sheet to block off the other openings and caulked the joints from inside the duct to seal.
https://www.rx7club.com/3rd-generati.../#&gid=1&pid=3
Lots of low hanging fruit on your setup. Good luck either way you choose to address it.
To pressurize the inlet you can extend the ducting into the bumper opening with some aluminum. The stock duct is incapable scavenging air from the bumper opening.
Here's a link to my thread with pictures of my ducting if you're looking for something to reference. I used aluminum sheet to block off the other openings and caulked the joints from inside the duct to seal.
https://www.rx7club.com/3rd-generati.../#&gid=1&pid=3
Lots of low hanging fruit on your setup. Good luck either way you choose to address it.
#18
Sponsor
iTrader: (41)
Any competent tuner will set the ecu to pull timing (and limit boost if the ecu is capable of it. The power fc cannot)) if certain parameters such as intake temps exceed a set threshold. 60C is hot. I personally won't even get on boost with those temps. You're asking for detonation. Any stock mount, regardless of size is going to have a difficult intake temps down. Because it sits directly on top of the radiator discharge, it heats up and never cools back down. Its a horrible design. If you add meth injection you can get away with it. Ideally you want to move to a vmount setup. It would also be a good idea to get a fast-acting intake temp sensor so you can see the temps in real time. The stock sensor takes forever to respond. This being said, it looks like something such as a solenoid is getting hot and acting up, defaulting you to wastegate spring pressure.
#19
Any competent tuner will set the ecu to pull timing (and limit boost if the ecu is capable of it. The power fc cannot)) if certain parameters such as intake temps exceed a set threshold. 60C is hot. I personally won't even get on boost with those temps. You're asking for detonation. Any stock mount, regardless of size is going to have a difficult intake temps down. Because it sits directly on top of the radiator discharge, it heats up and never cools back down. Its a horrible design. If you add meth injection you can get away with it. Ideally you want to move to a vmount setup. It would also be a good idea to get a fast-acting intake temp sensor so you can see the temps in real time. The stock sensor takes forever to respond. This being said, it looks like something such as a solenoid is getting hot and acting up, defaulting you to wastegate spring pressure.
#20
Rotary Motoring
iTrader: (9)
I have a track day coming up end of may
If you don't want to do that at least you could rig the system to spray water on the outside front of your intercooler.
That stock mount lower IC intercooler inlet piping can get pretty pinched and get even more pinched when soft/hot because its a close fit to the engine front pulley- any better pics of the pipes/couplings used there?
Just plugging the battery box hole and cross-over duct to the stock intake on the IC inlet ducting will help your IAC a huge amount lapping the track. I made a plug of soft foam for the battery box hole and used tape for the airbox cross-over.
#22
Keep the stock mount intercooler and add water. I am running 15 PSI on my stock twins with a Greddy SMIC and my intake air temps are low 30s max when running the smallest jet in the AEM WI kit (250cc/min). Perfect. Check out this video to see a shot of the engine bay and the track performance to get an idea.
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Dvst8 (04-18-22)
#25
Perhaps but I have tested the SMIC with the water off and those temps climb above 50c, so I know it's working as advertised.