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I recently bought a 1993 FD Touring. I will put the related mod list below. Since I have had the car, the weather has been pretty hot (91-98F), but the car seems like its been running hotter than it should be.
The day after I got it, I took it out for a nice Sunday drive up the Historic Columbia River Hwy (for those familiar with the Portland, OR area). Its a pretty tight road for the most part, and I'm still learning the car so I took it pretty easy, not getting into boost much. I noticed right when I got off my freeway exit to go there, the car was about 98C water temp, and in the high 50C intake temp wise (monitored on PFC commander) This seemed pretty high, but I knew these cars run a bit hot from the research I had done leading up to my purchase. It was also a 95F day. After actually getting to the fun road, I drove a few miles and noticed that my coolant temps had dropped into the low 90C range, but intake temp was still climbing higher to about 65C. I was still in the middle of the drive with no turn-arounds so I kept driving till I could turn around and go back home.
When I reached the area where I could turn around there was a bit of traffic, being a Sunday afternoon in a popular hiking area (Multnomah Falls), so I had to sit for a few minutes. By the time I was ready to go again, water temps had reached 101C and intake temps were at 68C. After getting on the freeway back home, both temps did not stabilize, they stayed roughly the same. freeway speed was about 60mph for about 7-8 miles. I then took my exit to go home and had quite qa few stop lights to sit at on the way. By the time I pulled into my driveway, water temp had reached 108C and intake temps were over 70C!! This is when I started to get freaked out. almost all of this driving was below 4k RPM, and I only did 2 WOT pulls early in the drive. I have observed the same results just daily driving to and from work which is about a 7 miles drive through town at no higher than 40 mph. On my commute, water temps have gotten as high as 100C and intake temps as high as 72C. This is just simple commuting, no pulls or high revs. I always warm the car up to 80C water temp before I leave
I am thinking maybe the IAT is getting heat soaked and giving a false high reading since the temps do not go down after you get moving, so I have ordered a fast reacting sensor in hopes that it will read lower when moving at speed. As for the water temps, I have no idea other than maybe a slow water pump or maybe a bad radiator. Both fans are running when you get out of the car, but I don't know what they are doing while I'm driving. I have also ordered a second oil cooler. The intake design seems like it just sucks in hot air, so id like to look at other options. I have not been able to find true cold air intakes for this car like you can get for other cars (filter outside the engine bay, like in the bumper or fender). I guess this is due to the design of the chassis.
Relative mods to car:
Pettit engine w/ 3mm apex seals (~50k miles on it)
Pettit Cool Charge 3 w/ duct
Pettit intakes
3in DP
Racing Beat catback
No cats
Radiator was replaced by previous owner, but I don't know what it is
Car seems to run fine, I just don't want to hurt anything. I plan to change all of the fluids this weekend, including coolant. Its just kind of weird to me, because I had the car inspected by Pettit before I agreed to purchase it and he said the car was a 12/10 mechanically. That's the reason I decided to get this one.
I apologize for the huge post, but if anyone has any advise or insight, I greatly appreciate it.
As for water temps....
100 C. isn't THAT hot. It's not ideal, but no need for panic. The stock thermosensor had a threshold of 101 C. to activate low-speed fans on the FD. Many of us have changed that with the S5 FC thermoswitch (P n P) which had a threshold of 95 C. https://www.rx7club.com/3rd-generati...u-read-397156/
There's also a way to change threshold on the PFC but you'll have to do a search.
If the car is new to you, change that coolant. I prefer the stuff for Asian cars, but I don't think it's a deal-breaker. Otherwise just green ethylene-glycol. Coolant should be changed in the car at least bi-annually IMO anyway. Leave as much DISTILLED water to the coolant ratio as you can get away with in your winters. For additional maintenance baseline T-stats aren't expensive and are easy to change (3 10mm bolts) while changing coolant. Stay with the STOCK Mazda T-stat and make sure to clock the jiggle-pin to 12:00. Don't under-drive the WP pulley. Some other things that can help is to stuff upholstery foam in the gaps around your radiator and IC duct when looking through the nose of the car.
Down the road you can search and consider a simple water-injection system for additional cooling along with other benefits. Dual oil coolers are worthwhile but I doubt you'll see anything dramatic reflected in coolant temps.
As for IAT's....
Those are a little hot IMO. I usually avoid hard boost on hotter days if I see anything in the high 40's C. Your IAT's are especially strange given that the PETTIT SMIC and duct is a pretty decent IC. You should have the divider in there to isolate the intake filters from hot underhood air. You might pull the IC and clean it. I use dish soap, hot water and a utility sink to do that once a year on my car. The stock sensor is slow to react and can heatsoak. I personally like the fast reacting sensor and relocate it post IC/pre-throttle body.
Make sure your belly-pan is in place and secure.
Side-note....
If you're on the stock twins make sure you have some type of boost -controller in place with that intake to avoid boost spike.
Also, a little concerned about the lack of a cat. The RB catback is PROBABLY enough back-pressure to avoid boost creep, but a cat, even a hi-flow cat is definitely enough. I prefer the sound with a cat and the lack of stink...but I'm old.
As for water temps....
100 C. isn't THAT hot. It's not ideal, but no need for panic. The stock thermosensor had a threshold of 101 C. to activate low-speed fans on the FD. Many of us have changed that with the S5 FC thermoswitch (P n P) which had a threshold of 95 C. https://www.rx7club.com/3rd-generati...u-read-397156/
There's also a way to change threshold on the PFC but you'll have to do a search.
If the car is new to you, change that coolant. I prefer the stuff for Asian cars, but I don't think it's a deal-breaker. Otherwise just green ethylene-glycol. Coolant should be changed in the car at least bi-annually IMO anyway. Leave as much DISTILLED water to the coolant ratio as you can get away with in your winters. For additional maintenance baseline T-stats aren't expensive and are easy to change (3 10mm bolts) while changing coolant. Stay with the STOCK Mazda T-stat and make sure to clock the jiggle-pin to 12:00. Don't under-drive the WP pulley. Some other things that can help is to stuff upholstery foam in the gaps around your radiator and IC duct when looking through the nose of the car.
Down the road you can search and consider a simple water-injection system for additional cooling along with other benefits. Dual oil coolers are worthwhile but I doubt you'll see anything dramatic reflected in coolant temps.
As for IAT's....
Those are a little hot IMO. I usually avoid hard boost on hotter days if I see anything in the high 40's C. Your IAT's are especially strange given that the PETTIT SMIC and duct is a pretty decent IC. You should have the divider in there to isolate the intake filters from hot underhood air. You might pull the IC and clean it. I use dish soap, hot water and a utility sink to do that once a year on my car. The stock sensor is slow to react and can heatsoak. I personally like the fast reacting sensor and relocate it post IC/pre-throttle body.
Make sure your belly-pan is in place and secure.
Side-note....
If you're on the stock twins make sure you have some type of boost -controller in place with that intake to avoid boost spike.
Also, a little concerned about the lack of a cat. The RB catback is PROBABLY enough back-pressure to avoid boost creep, but a cat, even a hi-flow cat is definitely enough. I prefer the sound with a cat and the lack of stink...but I'm old.
Thanks for the reply!
I just changed the coolant this weekend to distilled water and Prestone coolant flush to try and clean out any buildup there might be. The old coolant came out pretty clean though, so I don't know how much of an effect this will have. I will change it back to around a 70/30 water/coolant mix after i cycle it a few times. I did also discover that the radiator is stock, though it is a newer one and looks really clean. I still might just buy a Koyo and swap that in before I refill the system. I'm definitely going to look into the fan settings on he PFC though, Id like to lower it quite a bit if I can.
The intake temps are definitely what I was most worried about, especially since they just keep climbing and don't really come back down. I did get my fast reacting Triumph sensor installed over the weekend as well, but I ended up breaking my TPS in the process... The 25 yo plastic just cracked right in half while trying to unclip it. So now I have to track down another TPS before I can see if the IAT sensor changes anything.
The intakes do have the divider to keep them "isolated", but it doesn't seem to block them off enough. I'll wait and see what happens after I get the car running again and if I still get really high IAT's, and if i still am, I'm going to get getting a different intake and adding 50/50 AI. I don't really care about tuning the AI for more power just yet, Id just like it for peace of mind.
Also in regards to the catless exhaust, it does have a second muffler in the middle that keeps the sound more livable. Its actually not raspy or brappy at all except at WOT. I haven't noticed any boost creep on my gauge, but im not exactly focused on it during a pull either. the PFC doesn't read in PSI so idk what that reading translates to yet. I don't know if that adds much back pressure though... After I get the thing running good again, I plan to have it re-tuned. Its been about 4 years since the PO had it tuned at Pettit, and I'm running on slightly lower octane gas now. 92 as opposed to 93. Not much difference, but again, peace of mind...
I'll post an update after I find a new TPS and get the car running again.
If you're changing the IAT sensor, now might be the time to consider relocating it.
I would still consider a boost controller if you don't have one already. Especially with fall and cooler ambient temperatures right around the corner. 92 octane should be fine as long as you keep it at stock boost (or whatever max boost level it was tuned for). And on the PFC commander, .7 bar = 10 psi.
I changed out the iat sensor and it seems to have worked! It's are still a bit warm, but have t gone over about 55c since.
I also drained the coolant, and refilled with distilled water and coolant flush. I'll drain it out and refill with water/coolant this weekend. Water temps have not gone over 90c since refilling. Not sure if it's because there's more water in the system now, or just because it's fresh. Old coolant still looked "clean". Radiator is a newer stock unit, but I got a Koyo so that will also go in this weekend.
As stated in my last post, I broke the TPS removing the plug while trying to get to the it sensor... I replaced it with a known (tested) working sensor I got from a forum member (rotorhead racing) and it seems fine except for one issue. In between wot shifts, the car hesitates for a second before getting back into boost. Only last for about a second, but is very noticeable as the car makes no power for a second. This didn't happen prior to the new sensor. This only happens between shifts. If I am cruising at 3k and then do a pull, in any gear, it pulls hard and strong with no issue. Only when wot, shift, wot can it be felt. The car almost sounds like the box (pettit) may be stuck open for a split second. It's a air whoosh kind of sound (after the initial whoosh of the bov, but quieter), then back to power.
Could this be because I did not adjust the new sensor with a multimeter? I just set it up in the same position as the old sensor since it worked fine before I broke it, and the replacement was tested to work correctly. Or could it be that I possibly broke a vac line while in there and didn't notice? I was very careful so I don't think it's a vac line. I also didn't touch the bov so I don't think it decided to break while it sat for a week.
Don't know exactly, but since you lost the pressure reading in the pfc, maybe check the small vacuum line that goes near the Throttle Body to the pressure sensor (a small black box in red in the photo below ), it's so tiny that you may have unplugged it without noticing.
If your MAP sensor is not hooked up (pictured above), you'll know it (will run like ****).
A Koyo N-flow and upgraded SMIC will go a long way to helping get your temps down as well as a R1/R2 passenger oil cooler. Make sure you have an undertray and that the crossover hole from your IC duct is covered up, as well as the battery vent (assuming you have a stock IC).
And make sure you have a T-stat. Some people pull them thinking that helps cooling
@tomatoto I think I worded that poorly responding to SgtBlue. I didn't lose pressure on the PFC, I just meant that the reading isn't in PSI or BAR, its in mmHg. The TPS is a used factory one as far as I can tell. Looks exactly the same as the one that it replaced, other than a small difference in the font of the part numbers. I still have the original one if anyone wants it. I don't know if it still works or not. Its cracked where the plug meets the actual sensor. All the pins inside seem to be connected still. I just wanted to be safe and get a new one. Free to anyone who wants it, just pay shipping. Pics available.
I have a Koyo N-flo going in this weekend, along with new hoses and a new t-stat. I think my rad fans come on around 80c.
Already have a pettit cool charge 3 SMIC. I think one of the main reasons I still have relatively high IAT's is because of the Pettit intakes, but i could be wrong. Seems like they just suck in all the hot air that the rad fans blow into the engine bay.
Any input on the small hesitation between shifts? I'm going to check the reading with a multimeter this weekend just to try and see if that could be the case. I probably do need to adjust the TPS since its not the same one.
There isn't much more to say but it's vital that the cooling system is bled properly. It will spike up pretty fast if there is air in it. Generally, on my touring (in Oregon also) it sees around 185 to 190F for the water temps on a 90+ degree day on the stock cooling system. It settles at 176F during all the other times of the year. One thing that is very vital is your oil cooler. Tourings got jipped with one due to the auto tranny so upgrading to two should help negate some heat as oil does a lot of engine cooling. As for the air temps, you're kind of boned without going AI or a better intercooler and better ducting (Don't get a FMIC as they block the radiator). I run windshield washer fluid for cooling and it helps a ton for keeping temps near ambient when doing pulls.
... think one of the main reasons I still have relatively high IAT's is because of the Pettit intakes, but i could be wrong. Seems like they just suck in all the hot air that the rad fans blow into the engine bay
IMO, i true cold air intake is as important as a good intercooler. Do you have the heat shied that comes with the Pettit intakes that blocks the radiator? If not, recomend finding one or fabricating one. Also worthwhile to fab a shield to the turbos
Regarding the hesitation. Not sure if it it the TPS, but it's always good to check that it's w/i spec
IMO, i true cold air intake is as important as a good intercooler. Do you have the heat shied that comes with the Pettit intakes that blocks the radiator? If not, recomend finding one or fabricating one. Also worthwhile to fab a shield to the turbos
Regarding the hesitation. Not sure if it it the TPS, but it's always good to check that it's w/i spec
I do have the heat shield for the intakes. I haven't had much luck finding a true cold air intake for the FD other than the m2 replica stuff, if you call that a cold air intake... unless I'm missing something. Is there one you'd recommend? Most of the cars I've had in the past have cold air intakes available that mount the filter in the fender, completely out of the engine bay. This doesn't really seem like an option on the FD though.
Regarding the hesitation, I did find a loose vac line right next to the throttle that connects to the UIM. I will plug that back in and see if it helps today. Sort of feel let down regarding the vac lines on this car as I was told they (majority) were changed to silicone. From what I can see, maybe a few of them were. the rest are pretty stiff. I guess that's what happens when you buy something without seeing it first.
There isn't much more to say but it's vital that the cooling system is bled properly. It will spike up pretty fast if there is air in it. Generally, on my touring (in Oregon also) it sees around 185 to 190F for the water temps on a 90+ degree day on the stock cooling system. It settles at 176F during all the other times of the year. One thing that is very vital is your oil cooler. Tourings got jipped with one due to the auto tranny so upgrading to two should help negate some heat as oil does a lot of engine cooling. As for the air temps, you're kind of boned without going AI or a better intercooler and better ducting (Don't get a FMIC as they block the radiator). I run windshield washer fluid for cooling and it helps a ton for keeping temps near ambient when doing pulls.
Good to hear that from someone relatively local. refilling/bleeding really helped bring down my temps. around 15-20 degrees C on the high end. Granted, it hasn't been as hot outside lately as when I was seeing those temps.
As for dual oil coolers, I actually have another one at home i bought recently that I plan to install soon. I just want to get some AN lines made before I install.
Also have AI on my to do list. I just want to get the car daily-able for a while while I rebuild my other car for a permanent daily.
Cold air for the intakes is marginal. There's a space between the fender and the radiator, but you need to duct that, otherwise your just sucking in hot engine heat. The M2 does that, or you can fab your own. If you have the Pettit shield, all you need is a shield for the turbos. The hood acts as the top. It's not perfect. but it's a lot better than having your intakes suck direct from the engine bay. See post 68 below
