Performing Honda K24a3/AST5 6spd Conversion

lookforjoe

True Classic
Spoke with the tuner today - he explained a couple of things regarding interpretation of the data in the tables, but acknowledged that the issues need to be addressed in person, so I'm taking it to him on Sat to revise as needed to get it right. I feel a bit better about it with the plan in place
 

lookforjoe

True Classic
I went over a couple things today - following the tuner's advice I re-flashed the ECU with the new tune, then did the TPS calibration. Still had the sticky idle & no fuel cut on deceleration, so I re-adjusted the TPS - allowing a fraction more 'slack', as the TPS can pretension the butterfly & prevent full return. That seemed to do the trick - I now have an proper idle of 900rpm as he set it, fuel cut on deceleration, and no more surge. A little annoying, as I did just recheck the base TPS setting recently. Maybe I just didn't allow enough 'give'.

On to other things, I found the contact terminal for the AC compressor was flaky - the AC wasn't coming on all the time, and/or shutting off even when in the "Max AC" mode. I rewired the connection with a replacement terminal. AC now stays on, and seems to be functional - hard to gauge entirely as we were driving around with the top off & windows down.

Excessive coolant temps do seem to be the bane of my existence. driving around town, idling & with AC on, the coolant temp went up to 200ºF.
I have the fans set so that one comes on at reduced speed of the VW switch low temp setting, then the other comes on when higher temp is met - the problem is, in this weather the engine coolant temps run much higher than the rad. I need to wire the low speed fan so it also runs full speed once the motor hits 190º.
 
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kmead

Glutton for punishment
I went over a couple things today - following the tuner's advice I refreshed the ECU with the new tune, then did the TPS calibration. Still had the sticky idle & no fuel cut on deceleration, so I re-adjusted the TPS - allowing a fraction more 'slack', as the TPS can pretension the butterfly & prevent full return. That seemed to do the trick - I now have an proper idle of 900rpm as he set it, fuel cut on deceleration, and no more surge. A little annoying, as I did just recheck the base TPS setting recently. Maybe I just didn't allow enough 'give'.

On to other things, I found the contact terminal for the AC compressor was flaky - the AC wasn't coming on all the time, and/or shutting off even when in the "Max AC" mode. I rewired the connection with a replacement terminal. ACnot stays on, and seems to be functional - hard to gauge entirely as we were driving around with the top off & windows down.

Excessive coolant temps do seem to be the bane of my existence. driving around town, idling & with AC on, the coolant temp went up to 200ºF.
I have the fans set so that one comes on at reduced speed of the VW switch low temp setting, then the other comes on when higher temp is met - the problem is, in this weather the engine coolant temps run much higher than the rad. I need to wire the low speed fan so it also runs full speed once the motor hits 190º.


All in all good news.

The coolant side of things is worrisome. Cooling is two things, air flow and coolant flow. You are already head and shoulders above the existing fans so it is unlikely air flow is the issue. You are also managing the onset of signficant flow both for AC and low speed driving. Added to that the additional ducting to evacuate air out of the dog house.

Out of curiosity have you tried covering your new outlets out of the dog house to see if there is possibly reversion happening due to positive pressure in the wheel wells? (Which would be a real pisser)

Have you looked at the water temp into and out of the radiator?
Do you have any sense of the flow around the system? Not sure how to get a sense of this. There is a mathematical way to take the air volume, existing air temp and then the input and output temp of the piping in this case (actual temp sensors would be better) to then calculate flow. Sadly my engineering education ended well before getting into thermodynamics etc so I am of no assistance, no surprise :).

Then there is the other elephant in the room which is the water pump and its ability to move coolant, restrictions upstream along with the thermostat which others have suggested alternatives to.

Painful trying to resolve cooling issues on a system where making changes are so complex due to the restrictions in the space in the engine bay and getting things around the complex geometry of the engine itself.
 

dcioccarelli

Dominic Cioccarelli
Excessive coolant temps do seem to be the bane of my existence. driving around town, idling & with AC on, the coolant temp went up to 200ºF.
I have the fans set so that one comes on at reduced speed of the VW switch low temp setting, then the other comes on when higher temp is met - the problem is, in this weather the engine coolant temps run much higher than the rad. I need to wire the low speed fan so it also runs full speed once the motor hits 190º.

In my experience of cooling issues in X1/9s, once you have ruled out all the basic issues (blockages, etc.) the single biggest problem is the lack of flow at idle / low RPM. Having the flow rate proportional to engine speed is always going to be sub-optimal (this can be rectified by using a electric water pump and the associated controller). A simpler modification is to change the pulley size on the pump.

In a Honda application, the pump was designed to move a smaller volume of coolant over a shorter distance: as a result, it won't be optimised for a configuration where the radiator is a long way from the pump.

Cheers,
Dom.
 

lookforjoe

True Classic
All in all good news.

The coolant side of things is worrisome. Cooling is two things, air flow and coolant flow. You are already head and shoulders above the existing fans so it is unlikely air flow is the issue. You are also managing the onset of significant flow both for AC and low speed driving. Added to that the additional ducting to evacuate air out of the dog house.

Out of curiosity have you tried covering your new outlets out of the dog house to see if there is possibly reversion happening due to positive pressure in the wheel wells? (Which would be a real pisser)

Have you looked at the water temp into and out of the radiator?
Do you have any sense of the flow around the system? Not sure how to get a sense of this. There is a mathematical way to take the air volume, existing air temp and then the input and output temp of the piping in this case (actual temp sensors would be better) to then calculate flow. Sadly my engineering education ended well before getting into thermodynamics etc so I am of no assistance, no surprise :).

Then there is the other elephant in the room which is the water pump and its ability to move coolant, restrictions upstream along with the thermostat which others have suggested alternatives to.

Painful trying to resolve cooling issues on a system where making changes are so complex due to the restrictions in the space in the engine bay and getting things around the complex geometry of the engine itself.

Thanks Karl.

The ducts are working - at idle, with fans on & the wheels turned, you can feel the hot air blowing out the duct into the wheel well.

I haven't checked coolant temp at the rad. The rad I/O temps are definitely lower than at the motor, simply based on the fact that the high temp fan doesn't kick on until the head temp is slightly over 190degrees F. I can't recall the temp values for the VW sender, I'll have to check. The fact that I actually only have one fan running full speed is not helpful, so that aspect I need to address.

I can test the stationary heat soak aspect by driving with the engine lid open & see if that makes a significant difference. I can also try removing all the airguides/deflectors I made that cover the underside forward and onto the subframe.

It could be that the water pump just doesn't push the volume needed at idle to compensate once heat soak sets in. The engine temp drops quickly once moving, even at low speed, so it seems to be a combination of air speed & flow. Peter did say that his works fine with the stock water pump, once he resolved the t/stat issue.

I'll start with figuring out an additional ground for the first fan that puts it to full speed when the higher temp is reached. EDIT - can't find my diagram now, this is from DeWolf (just 2 fans on mine, vs. one combo speed)- you can see the one fan will only run at low speed no matter what, as currently wired

referencing earlier threads on fan supply #1 #2

Electric fan setup.jpg
 
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kmead

Glutton for punishment
I am with Dom, if you can get the airflow at low speeds, then getting coolant volume is going to be key. Moving more coolant will give you more opportunity to get to where you want to go.

One of those thermostat guns can be pretty instructive.
 

lookforjoe

True Classic
I am with Dom, if you can get the airflow at low speeds, then getting coolant volume is going to be key. Moving more coolant will give you more opportunity to get to where you want to go.

One of those thermostat guns can be pretty instructive.
Are you sure 200* is a problem? My recollection is the stock fan on the Acura is set to come on at 207*.

So, I have determined that having only one fan running full speed was my primary issue - however, when idling with the AC on, in traffic, the coolant temp will sit at 200, then drop once moving. When moving, the temp stays consistently at just under 190ºF - which makes sense. It will drop further at high speed, but about 185ºF seems to be the normal temp. The full speed switch doesn't activate until the engine temp is over 190 - the temps at the rad output are clearly at least 10-20ºF cooler, since the switch rating is 82c for the high speed. The high speed fan setting turns OFF when coolant temp returns to approx 190ºF. I guess I would need to move the thermoswitch closer to the head if I want to lower the fan onset, unless there is an even lower fans switch than the 75/82ºC I bought...

As Mark pointed out 200ºF is NOT abnormal for the K24 - looking online, they can run hotter than that at idle. I'm just not sure I can get used to looking at the needle rising over 190ºF - with all the issues I've had in the past....

Anyway, the easiest way in my case to resolve the fan speed issue was to add a second relay & reroute the #1 low speed ground & feed to the #2 spots on the additional relay. The main relay feeding the fans is a 30A dual-throw relay, so I just added a new feed to the 5th pin

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black wire was the #1 (low speed) motor feed - white wire was the #1 ground via VW thermoswitch. Forgot to take pic of the 2nd relay in place

PXL_20210610_192732674.jpg
 
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lookforjoe

True Classic
Just adding this info here so I don't forget again. In typical driving, I leave for work (6:10-15am) when ambient temps are relatively low (for any given day). The coolant temp doesn't get anywhere near normal if I leave immediately & drive the 15 miles or so to work, mix of highway & local roads with numerous traffic lights. I can make the coolant temp rise more rapidly by keeping the cruise (light load, part throttle) rpm at 3K - so there is still a tune issue there.

This morning, I let the car sit idling after I arrived at work, to check the fan onset. Today, with ambient temps around 72F, the coolant temp (on the gauge) rose to 200 BEFORE the low temp fan kicked in - the high temp fan kicked very shortly thereafter. I (laid on the ground &) felt the I/O of the rad hoses before the fans came on, a few minutes after stopping, and it was easy to tell the t/stat was not fully open - the outlet was much lower temp to the touch. As soon as the outlet temp rose (indicating to me that the t/stat had finally opened fully), the fan kicked on. I was initially concerned that the fan circuit was dead - thought maybe I forgot to upgrade the fan circuit fuse.

I'll have to repeat this when the ambient temps are back up to the 90's. Again, this may all be worry for nothing, given these motors typically run close to 200F, however I don't want to wait until the temps are consistent high 90-100F to find out I have a real problem. Once it heat soaks, it is difficult to get the temp to drop rapidly.

It does seem like flow at low rpm is a concern - if the flow were greater, surely I wouldn't see such a large temp disparity in the cooling system - the hotter engine coolant would be passing through the rad at a greater rate.
 
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jimmyx

True Classic
I've battled similar cooling issues on various builds over the years and sometimes it's helpful to start at square one. If the coolant temp stays within normal range while underway, it's generally indictive of a properly sized radiator and sufficient airflow over the core. If the temperature rise occurs at idle, it is generally an air flow issue. The first thing to note is that driving 15 miles in 70 degree ambient temperature and not having a fully open thermostat doesn't sound right. Under those conditions, the thermostat should be fully open in a mile or two. I'm assuming the temp gauge sender is located on the engine? Are the fan triggered from a sensor located on the engine, or on the radiator? It would probably be helpful to take a thermo-gun reading on the engine side and at the inlet and outlet of the radiator to verify the actual temp in each location. To do a quick test, I would wire a toggle switch to manually trigger both fans at idle. As you noted, once heat soak is allowed to set in, it can be a bear to bring it back down. Coolant flow may also be an issue, but it's a delicate balance as too much flow can push the coolant through the core too quickly and hamper heat transfer. I would agree that the heat rise at 3K rpm is an engine issue. Something is causing excessive engine heat generation in that range and it's doubtful to be cooling system related. It might be tune, or it might be mechanical. If there is a slight head gasket leak, the temperature rise can be overcome with increased airflow over the core at higher driving speed too. Hopefully you'll get this all sorted in short order!
 

kmead

Glutton for punishment
I would agree with Jimmyx around the car being at operating temp within a few minutes/miles of driving off. My Element provides heat and registers normal operating temp within two miles from home on a mild morning.

Even at a low flow condition the thermostat should be opening relatively quickly, it shouldn’t be hanging. I could easily see the fan not starting until the system starts saturating which could take a few circulations particularly if the thermostat isn’t opening properly. Meaning it is allowing a small amount of coolant to run through the radiator which can handle it without the fan sensor getting to temp.

Would it be possible to pull the internal thermostat and try the Fiat three way thermostat from a 124 twincam as was suggested previously? I know not easy and likely need some extra piping to accommodate it.

Lack of fluid flow could well be an issue regardless but ensuring the thermostatic regulation side seems like it needs to be solved first.

It is a wives tale that too much flow through the radiator will hamper heat transfer, particularly if you are also pulling lots of air through the radiator.
 

lookforjoe

True Classic
I've battled similar cooling issues on various builds over the years and sometimes it's helpful to start at square one. If the coolant temp stays within normal range while underway, it's generally indictive of a properly sized radiator and sufficient airflow over the core. If the temperature rise occurs at idle, it is generally an air flow issue. The first thing to note is that driving 15 miles in 70 degree ambient temperature and not having a fully open thermostat doesn't sound right. Under those conditions, the thermostat should be fully open in a mile or two. I'm assuming the temp gauge sender is located on the engine? Are the fan triggered from a sensor located on the engine, or on the radiator? It would probably be helpful to take a thermo-gun reading on the engine side and at the inlet and outlet of the radiator to verify the actual temp in each location. To do a quick test, I would wire a toggle switch to manually trigger both fans at idle. As you noted, once heat soak is allowed to set in, it can be a bear to bring it back down. Coolant flow may also be an issue, but it's a delicate balance as too much flow can push the coolant through the core too quickly and hamper heat transfer. I would agree that the heat rise at 3K rpm is an engine issue. Something is causing excessive engine heat generation in that range and it's doubtful to be cooling system related. It might be tune, or it might be mechanical. If there is a slight head gasket leak, the temperature rise can be overcome with increased airflow over the core at higher driving speed too. Hopefully you'll get this all sorted in short order!

Thank you for the input!

So, Going back to last November - the coolant temp was going over 200ºF before the (185ºF) t/stat would open. I determined the t/stat housing offset created approx a 20º differential. Using a 160ºF T/stat resolved that issue. The t/stat and cooling system layout is functionally the same as the stock TSX layout - just offset from the main water housing. Once the t/stat was addressed, Idling temps were a non-issue in the cooler months.

I have heat within a few miles of driving, (same range as my C30 or the Volvo wagon) just t/stat doesn't open fully unless I let it idle.

Temp gauge sender is in the water housing on the head. Rad fan thermoswitch is in the rad, stock location.

Using a laser temp gun, temps in the head match the gauge. I don't recall the temp values I recorded at the rad I/O at 190º engine temp. It's safe to say the outlet temp is around 170ºF, as that is when the lower temp switch activates.

The 3K issue I'm sure is in the tune, I can keep the coolant temp down by driving at lower or higher rpm

I let the car idle for about 1/2 an hour this evening, whilst I was charging the AC, and the coolant temps stayed right at 190ºF - however ambient temps were only in the high 60's when I was working on it.

Mainly, it's frustrating that the operating temp deviates so much with the ambient temp variations, I'd just like it to be more uniform like my other cars 🤣
 

lookforjoe

True Classic
Another issue that arose after my round trip to Carlisle, PA - the AC compressor mount on the intake plenum broke again - I didn't have good weld penetration. having the compressor vibrate around cracked the high side fitting I made - replaced it with the ones in my hand. I made a new support bracket attached to the main bracket welded to the plenum (no pics)

PXL_20210611_001958686.jpg


Cut the line & installed the new line fitting

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cracked fitting

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new line installed, drew system down & recharged

PXL_20210611_220124614.jpg
 

jimmyx

True Classic
Airflow usually has the most significant impact on idle temp. On the next hot/humid day, I would still try manually engaging both fans once the temp gets to 180 and see if it will hold it in check. Assuming that the thermostat is operating correctly and the entire system is bled it will either confirm or eliminate airflow as a contributor. On the 3K issue, curious to know what the AFR reads at a steady cruise, and if it only happens at high ambient or occurs regardless.
 

lookforjoe

True Classic
Airflow usually has the most significant impact on idle temp. On the next hot/humid day, I would still try manually engaging both fans once the temp gets to 180 and see if it will hold it in check. Assuming that the thermostat is operating correctly and the entire system is bled it will either confirm or eliminate airflow as a contributor. On the 3K issue, curious to know what the AFR reads at a steady cruise, and if it only happens at high ambient or occurs regardless.
Thanks Jimmy - good diagnostic suggestion - I'll have to add a wire to make an override for both fans - I added one years ago that operates the AC fan.

The 3K issue happens regardless of ambient temp - it did it yesterday morning w/ amp temp of around 60, and going to/from Carlisle when it was 80s-90's. I'm going back to the Dyno tuner this evening, so I will have him investigate it. AFR's on the wideband are where one would expect for cruising (steady rpm/light throttle) - around 14.7
 

lookforjoe

True Classic
So.... After the visit to the Dyno.... before I forget - the biggest issue (in terms of power) is the exhaust - I have too much back pressure, which kills the VTEC up top, which is why he set the cam advance to 20º max. The other element here his that the AFR's from the system WBO2 don't jive with the AEM WBO2, which he says is also due to the back pressure. The way to confirm this is too remove the cat & do a pull - if the cat is the cause of the restriction, the system WBO2 should register leaner AFR's and match the AEM WBO2 more closely. The rest of the exhaust is 2.5", which is more than enough for my HP range.

He witnessed the 3K issue - you can watch the STFT values climb at a constant, light load 3K setting, as the system tries to compensate and the coolant temp rose about 8 degrees over the short test run. He is unsure what is causing that. He is concerned about the possible oil contamination. I need to do another leak down test & see where my oil is coming from.

Besides that, the coolant temps were rock solid during the Dyno session. He said temps of 190-210 are perfectly within normal parameters, so maybe I need to let it go & not worry about the idle temp. I'm still going to hook up the second fan to a bypass & try running both fans though.

He recommends GESI cats - so I'm going to look into that, I'll make a test pipe in the meantime to check. The cat I have is a generic 2.5 400 cell (claimed) I bought off Amazon.

The GESI cats are only 4" body (I'm guessing about 8" total) -

Screen Shot 2021-06-12 at 10.13.24 PM.png


pic of the current cat (11" total):

IMG-20191202-135947.jpg
 
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jimmyx

True Classic
So.... After the visit to the Dyno.... before I forget - the biggest issue (in terms of power) is the exhaust - I have too much back pressure, which kills the VTEC up top, which is why he set the cam advance to 20º max. The other element here his that the AFR's from the system WBO2 don't jive with the AEM WBO2, which he says is also due to the back pressure. The way to confirm this is too remove the cat & do a pull - if the cat is the cause of the restriction, the system WBO2 should register leaner AFR's and match the AEM WBO2 more closely.

He witnessed the 3K issue - you can watch the STFT values climb at a constant, light load 3K setting, as the system tries to compensate and the coolant temp rose about 8 degrees over the short test run. He is unsure what is causing that. He is concerned about the possible oil contamination. I need to do another leak down test & see where my oil is coming from.

Besides that, the coolant temps were rock solid during the Dyno session. He said temps of 190-210 are perfectly within normal parameters, so maybe I need to let it go & not worry about the idle temp. I'm still going to hook up the second fan to a bypass & try running both fans though.

He recommends GESI cats - so I'm going to look into that, I'll make a test pipe in the meantime to check. The cat I have is a generic 2.5 400 cell (claimed) I bought off Amazon. The GESI cats are only 4" body -vs. the at least 6" or more of the current cat (11" total)
STFT climb at exactly 3K and at no other time, accompanied by a rise in temp is truly the puzzle palace. Very curious about the outcome. Most all the common causes wouldn't normally be present in such a narrow range, so the answer to this should be quite the learning experience. Not clear on what pointed him to think about oil contamination? Finding signs of oil or just a precaution?
 

lookforjoe

True Classic
STFT climb at exactly 3K and at no other time, accompanied by a rise in temp is truly the puzzle palace. Very curious about the outcome. Most all the common causes wouldn't normally be present in such a narrow range, so the answer to this should be quite the learning experience. Not clear on what pointed him to think about oil contamination? Finding signs of oil or just a precaution?

The oil smoke at idle when sitting. Goes away under load, at least not visible. I need to do another leak down to see where the source is. I have no CC pressure issue - the head vent is clear & no evidence of oil blow by into the vent filter, so it would seem more likely valve seals than rings, which truly sucks since those were all just replaced with Honda-packaged seals when the K20Z3 head was refurbished. I'm not removing the engine (again) anytime soon, so I will have to live with the oil consumption for the time being.

I watched him play with the fuelling values in the specific lightest load range (very bottom of the range) - you could watch the trim drop back down - but he couldn't leave it like that at it would cause tip-in fueling issues. I'm going to deal with the exhaust (and AFR-related load issues) first. I can just avoid the 3K rpm range in the meantime.
 

Rodger

True Classic
FWIW, I took mine out for a drive today to see how my temps were doing. I got it up to operating temperature then parked it in my garage and just let it idle while I was datalogging to watch the actual engine coolant temperature. When I parked it after the drive the ECT was 193. After idling for a while it climbed up to 199, then 202 (display color in K Manager changes from green to red), 204 and as soon as it hit 206 the radiator fan kicked on. I have the MWB aluminum radiator with two stock Fiat fans, one connected to a standard temperature range sensor in the radiator and one for the AC system. I have it wired for only one radiator to kick on with the temperature sensor, so stock wiring. The fan ran for a few minutes and the ECT came down first to 204, then the fan shut off and the ECT continued to drop until it was back to 199. I let it cycle several times with same result. The only thing I can conclude from my experience is that the Honda water pump seems to be capable of pushing the coolant the distance to the front radiator. And I used the K-Tuned upper coolant housing that has a rather small bore, much smaller than the diameter of the under car coolant pipes. It was nice to hear that your tuner guy says these engines can go up to 210 and still be in a normal range.

Good luck with your hunt for the remaining gremlins.
 

lookforjoe

True Classic
FWIW, I took mine out for a drive today to see how my temps were doing. I got it up to operating temperature then parked it in my garage and just let it idle while I was datalogging to watch the actual engine coolant temperature. When I parked it after the drive the ECT was 193. After idling for a while it climbed up to 199, then 202 (display color in K Manager changes from green to red), 204 and as soon as it hit 206 the radiator fan kicked on. I have the MWB aluminum radiator with two stock Fiat fans, one connected to a standard temperature range sensor in the radiator and one for the AC system. I have it wired for only one radiator to kick on with the temperature sensor, so stock wiring. The fan ran for a few minutes and the ECT came down first to 204, then the fan shut off and the ECT continued to drop until it was back to 199. I let it cycle several times with same result. The only thing I can conclude from my experience is that the Honda water pump seems to be capable of pushing the coolant the distance to the front radiator. And I used the K-Tuned upper coolant housing that has a rather small bore, much smaller than the diameter of the under car coolant pipes. It was nice to hear that your tuner guy says these engines can go up to 210 and still be in a normal range.

Good luck with your hunt for the remaining gremlins.

Thanks for the input, Rodger.

I also used the K-Tuned upper housing (the one on the back side of the head) to connect to the t/stat/water housing - I was also concerned about the very small passage, however it does seem to be an non-issue.

The other thing the tuner suggested (if I really wanted to do it) was hooking up the ECT control ground for the rad fans - to use the engine temp to govern onset vs. rad temps. At this point, running an extra wire (neatly) in the loom from the bay back through the cabin and on to the front of the car would be more work than I care to do. Maybe I'll run supplemental harness inside the water tunnel ..... He did also say though, he tracks his K24/K20 motor & can see 220-240 temps, while far from ideal, he was not concerned about the motor suffering/ performance loss simply because the operating temps climbed that high.

On the exhaust, I tried looking for your post regarding the muffler - I recall you found a quieter muffler - how is that performing? Have you driven the car hard to put the VTEC to the test? Did you Dyno your setup, I don't recall. EDIT. - found the post - had to go through several pages of your post history - can't select "threads by xxx" in the User CP.
 
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