[info] Toyota SW20 MR2 Kswap

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Captainavi
Posts: 6
Joined: Tue Nov 16, 2021 10:44 pm
Github Username: Captainavi
Slack: Avi Moore

Toyota SW20 MR2 Kswap

Post by Captainavi »

(Mistake) Duplicate Post. Next post is real.
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Last edited by Captainavi on Wed Nov 17, 2021 8:42 pm, edited 2 times in total.
Captainavi
Posts: 6
Joined: Tue Nov 16, 2021 10:44 pm
Github Username: Captainavi
Slack: Avi Moore

Toyota SW20 MR2 Kswap

Post by Captainavi »

Hello,

I am building a K swapped 1991 Toyota Mr2 with a K24A2 engine and a 2015 6 speed Civic SI transmission.

I purchased this car specifically for this project to eventually be a daily. When I got the car the stock motor was run down and needed a significant amount of work but it did run. The transmission had some issues and the axle seals were leaking slightly. (Probably the culprit) The largest problem was one of the axle boots had gotten destroyed at some point before I got the car and the CV with no grease had gotten destroyed. I drove the car for about 2 months until the noises from the CV were too much to bear. Pulled the motor replaced brakes and all suspension bushings.

This project was originally supposed to run with a stock Honda ECU and Hondata tuner device. After failing to get the ecu working with all of the stupid Honda immobilizer tech I decided to move over to RUS.

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The engine mounts are from Hux Racing. They are not intended to work with this transmission combo, all but one mount fit up perfectly. I was able to attach the last one (rear mount from crossmember) with an additional adapter bracket I made out of some thick aluminum angle stock.

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Using KTuned thermostat housing and fill neck in order to adapt to AN and give me a little more freedom with how I route the hose. Since the MR2 has long stainless coolant lines that run from back to front I brazed some stainless AN -16 bungs onto the ends. This made it easy to connect the coolant with short lengths of hose. Although the cost of the AN was a bit painful I think it was worth it for the ease of removal.

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Got axles from Driveshaft Shop based on the MR2 SW20 NA Level 2.9 for the Hux Racing mounts. Since my transmission is different from the Hux racing setup I had to get them with custom length. They seem to fit well. Nothing is leaking from my axle seals so far.

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Using a stainless exhaust header I found on ebay for only 50 bucks back in the beginning of the build. I figured it was worth a shot even if it was crap for that cheap. It is pretty thin metal as expected but not terrible. The welds are are surprisingly good for the money, only a few leaks that I was able to seal up. May crack in the future but it gets me started until I can make a custom one.

The exhaust on the MR2 5FSE comes out of the front of the engine and the K24 exits on the rear some the spacing is very tight. I wanted to use the stock barrel muffler for the OEM look and hopefully OEM volume. From factory it only used 2" exhaust pipe all the way into the barrel. Decided to try and drill out the muffler and replace the internals with 3 inch stainless pipe so I could run 3" all the way and get a little more flow out of the barrel. The exhaust has been taking the longest because I had no previous experience TIG welding. I bought myself a TIG machine a few months ago and I have been teaching myself to weld stainless in order to do the exhaust. At this point I have nearly finished it just need to finish up the backside of the input pipe and weld the top patch on.

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That is pretty much where I am at right now. I have most of the engine wiring harness done as well but I don't have any electronic diagrams to post here yet. As soon as the exhaust is done I will be jumping into finishing the wiring and I will try to post some more updates here as I work through it.

Plenty of stuff done to this car not discussed here yet. Let me know if you have any questions about the build.

Here is how the bay looks right now. Pretty dirty right now, unfortunately the car has had to sit under a cover outside and it has been raining recently.
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mck1117
running engine in first post
running engine in first post
Posts: 1493
Joined: Mon Jan 30, 2017 2:05 am
Location: Seattle-ish

Re: Toyota SW20 MR2 Kswap

Post by mck1117 »

Damn, that thing is CLEAN! Too nice for rusEFI!
mk e
Posts: 486
Joined: Tue Dec 06, 2016 7:32 pm

Re: Toyota SW20 MR2 Kswap

Post by mk e »

Yes, very clean and very neat work on the swapt.

Question, 3" exhaust is good for...400+ hp, is there a turbo coming you forgot to mention? :)

If not, I have 1 small concern. It looks like the 3" comes off the header which is basically the same size with no real merge or choke, am I seeing that right? If so, that means your collect length is effectively everything from where the 4 pipes join to the dump into the muffler which is quite a long collector and would want to be a tuned harmonic length for best performance. The alternative is add a choke to set the tuned length.

Nice project
Captainavi
Posts: 6
Joined: Tue Nov 16, 2021 10:44 pm
Github Username: Captainavi
Slack: Avi Moore

Re: Toyota SW20 MR2 Kswap

Post by Captainavi »

mk e wrote:
Wed Nov 17, 2021 1:47 pm
Yes, very clean and very neat work on the swapt.

Question, 3" exhaust is good for...400+ hp, is there a turbo coming you forgot to mention? :)

If not, I have 1 small concern. It looks like the 3" comes off the header which is basically the same size with no real merge or choke, am I seeing that right? If so, that means your collect length is effectively everything from where the 4 pipes join to the dump into the muffler which is quite a long collector and would want to be a tuned harmonic length for best performance. The alternative is add a choke to set the tuned length.

Nice project
Probably a turbo coming at some point. Certainly has crossed my mind more then once. :lol:
Main reason I went for the 3 inch was to leave room for that once I get up a running.
I want to get on the road before I get too ahead of myself.

I'm not sure if I completely understand your concern. The output of the header is 2.75 inches then there is a reducer that adapts to 3 inches after that.
Would the collector need a restriction afterwards where the dia reduces and then goes back to 3 inch with a taper? What would a choke implementation look like here?

In the future when I go turbo I will be making a custom header to replace this Chinese one, at that point I can make the collector output whatever size I need.
mk e
Posts: 486
Joined: Tue Dec 06, 2016 7:32 pm

Re: Toyota SW20 MR2 Kswap

Post by mk e »

Captainavi wrote:
Wed Nov 17, 2021 9:09 pm

I'm not sure if I completely understand your concern. The output of the header is 2.75 inches then there is a reducer that adapts to 3 inches after that.
Would the collector need a restriction afterwards where the dia reduces and then goes back to 3 inch with a taper? What would a choke implementation look like here?
Well the problem will be solved once you get the turbo ;)

I'm talking about the way headers work to help you make hp. You have a pulsing flow in the exhaust with the pulse freq equal to rpm/2. Then the tubes have their own natural frequencies that that will "ring" at and when a natural freq or harmonic match the engine pulse freq you get some extra work being done to create a vacuum to help pull in more air into the cylinders and you get more hp. Its different but you can think of it like an organ pipe...a longer pipe is a lower natural freq because it takes the wave which is moving at the speed of sound to get to the eng and bounce back. There is a wave reflection any place there is an abrupt change in cross-sectional area...so where the primaries enter the collector and in your case again where the 3" pipe dumps onto the muffler.

You have an 8k? engine....those are primaries are quite short, they are tuned to be on probably the 4th harmonic (really 4th reflection) at 8k so they are also in tune at 2k, 4k, 6k , you get the 6k point because its reflections not truly harmonics. most race headers are tuned to the 3 reflection as that generally provided the best balance of wave power (they get smaller each reflection vs pipe flow loss (longer is more restrictive). 8k is already the 4th reflection so 6k is the 5th, 4k the 6th, 2k the 8th and there is very little energy left to reflect at that point so the primaries in you case are helping the most at 8k and doing basically nothing below 4k....an that is where the collector comes to the rescue. The collector is normally tuned to pull up the bottom end. Typically you see the 4th, 5, 6th reflection used at peak rpm....so for you lengths around 24, 15, 8...just guessing, but you effectively have abpout 48-60" it looks like so you will be tuned to like the 1st or 2 reflection to an to kind of unknown rpm, but lets you you hit the 1st reflection at 8k, that means there are no pulses below that to help boost your low-end HP.

The way you fix that is with what is caller a choke. A choke is a diameter reduction that you put in define your collector length. it had a quick reduction followed be a gradual expansion and is sized so it doesn't really hurt flow much (small but very short length) but it effectively terminates the waves so nothing that comes after counts in the tuning, it just flow restriction.

when you see something the looks like this, that reduced OD section is a choke
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This is my engine at 9k as an example the bottom graph, the red line is the exhaust pressure waves bouncing around in the simple header with primaries and collector. When you go to something like a tri-y design you get more tuned rpms points but generally a bit more flow restriction so flatter hp curve but slightly lower peak hp vs a 4into1.
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Captainavi
Posts: 6
Joined: Tue Nov 16, 2021 10:44 pm
Github Username: Captainavi
Slack: Avi Moore

Re: Toyota SW20 MR2 Kswap Update and Request for Help

Post by Captainavi »

Finished the muffler. Certainly not going to win any awards!
I think it should work though, there isn't any leaks for the time being.
The muffler is doubled layered and it is impossible to clean in between the two layers so when welding all the junk gets pulled into the weld.
It is all bolted up now and everything still fits well.
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All of the essentials are wired up to the MRE and verified working with the exception of triggering.
Having trouble getting the triggering to work. I am not sure if my configuration is supported by default.
My cam trigger wheel and crank trigger wheel are both listed in the rusEFI supported triggers page but they are listed separately.
I was able to retrieve this from the engine sniffer for the cam wheel. The crank is a Honda K 12+1 wheel.
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According to the Haltech data page about K24 triggering the exhaust cam sensor is used for home signal and the crank is used for the actual crank sync.
The intake cam is used for VVT but I am not worried about that right now.
https://support.haltech.com/portal/en/kb/articles/thomas-te#Trigger_System

Does anyone know if using the exhaust cam in this way is supported and if so how to configure it in TunerStudio?
With only the crank selected under Honda K 12+1 I was able to see the triggering in the high speed graphing but it was irregular and did not seem correct.
Under all other settings I was not able to read anything from the high speed graph in TS.
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