Performing Honda K24a3/AST5 6spd Conversion

[kmead]

Only spent a short time on it today - just cleaned up the wiring to the various solenoids and sensors that are now too close to the header. Extending the wire to the oil pressure sensor, routing it behind & under. Heat sheathing added on that.

Do you have any images of the headers in place with a view across the rear structure, a clear top view of the trunk with them in place or other images which would show the intrusion and how much space you would have under the cut out section. Any dimensions of clearance to the removable section?

My first notion is creating a a closure for the antlers left over from the strut towers to stabilize the openings. Perhaps place a couple of weldnuts on the reverse side (or enough material thickness) to provide a strong feature to draw the assembly closed. Adding a thicker section (12ga) to the underside of the removable section and plug welding the the thin steel to it would give you a way to then add some returns to then run fasteners into the weld nuts. the returns outside surfaces would be flush with the ends so you aren’t really drawing the parts together, juse mating them.

Any opportunity to have a vertical return on the trunk side?

We had talked about a box section on the trunk side, could that still work? If there was a wider box on the trunk side to then tie into the vertical flange off the strut towers. This assembly would approach the opening from the trunk side, bolt to the antlers to lock the overall width and depth and then bolt in near the strut towers from the trunk side. Likely need to weld in a doubler to the areas near the strut towers to get enough thickness of the steel to get three threads into (generally one tries to get a minimum of three threads into the steel).

 

[lookforjoe]

I don't have any measurements yet. I gave the header to my local expert welder to get into a few places I just couldn't reach and/see to weld properly. I should have it back today, hopefully. I can then install it & take some reference pics to determine offset/height etc.

I started sketching ideas for securing the top plate, and an insertable cross brace that may/may not be welded in place, depending on whether I can pivot the header under it to install. 1" Square tube is more likely to work for that, the 1.75" round tube will interfere, I'm pretty sure.

Reinforcements with welded nuts was my plan for the top plate - either protruding tongues on the existing structure or one male one female on the removable plate so it can be tucked in & placed. I may actually be able to weld it back, however I think I like the extra access with it removable.

Inner wall I should be able to make a box section akin to the air duct for the extractor fan in depth - I don't think it needs to be much deepr than that, however I will confirm once measurements are taken. I'll deal with that part last.

Three locating bolts/nuts makes more sense than the two I have in my drawings - I can see how that helps eliminate twist/movement in the junctions

 

[kmead]

I will reply to this later. I would start with CAD to solve this (cardboard aided design) to range the solution.

I don’t see using a tube in the design either square or round and I don’t really think it is needed as the engine is no longer applying load to the crossmember up there, it is really transferring load from the left side to the right side.

I presume the mount for the rear deck spring can go?

 

[kmead]

It is a bit unclear as to the actual intrusion of the header into the trunk and how high

I was thinking fillers going into the cut ends of the structure to fill them and provide a place to run fasteners in to tie the two sides of the structure together.

The top cover would have a heavier gauge part welded to it (plug welded) with returns for the fasteners into the fillers

Lastly the boxing of the section that runs into the trunk would encapsulate the rear most section of the header tubes and extend past the top filler section to then bolt into the heavier gauge near the strut towers.

 

[lookforjoe]

I will reply to this later. I would start with CAD to solve this (cardboard aided design) to range the solution.

I don’t see using a tube in the design either square or round and I don’t really think it is needed as the engine is no longer applying load to the crossmember up there, it is really transferring load from the left side to the right side.

I presume the mount for the rear deck spring can go?

This earlier pic gives a good indication of the overall height - I can add the square tube at the top & use that to support the top plate without interfering - that will also give me a vertical surface to bolt a new inner plate to

This is a 18ga panel I folded back when testing the bench sheet metal press. I think that's about as deep as it may need to go

 

[lookforjoe]

It is a bit unclear as to the actual intrusion of the header into the trunk and how high

I was thinking fillers going into the cut ends of the structure to fill them and provide a place to run fasteners in to tie the two sides of the structure together.

The top cover would have a heavier gauge part welded to it (plug welded) with returns for the fasteners into the fillers

Lastly the boxing of the section that runs into the trunk would encapsulate the rear most section of the header tubes and extend past the top filler section to then bolt into the heavier gauge near the strut towers.

Nice! Thank you Karl - I had not considered that approach. The only issue is the right side is cut back on a diagonal, so it will be tricky to make a filler plate - it can't be flat as the header angles in to that area. I'll have to play around with that.

I want to keep the stock trunk lid spring mechanism if possible. I kept the ears attached to the top plate for now.

 

[kmead]

Nice! Thank you Karl - I had not considered that approach. The only issue is the right side is cut back on a diagonal, so it will be tricky to make a filler plate - it can't be flat as the header angles in to that area. I'll have to play around with that.

I want to keep the stock trunk lid spring mechanism if possible. I kept the ears attached to the top plate for now.

I thought you had pneumatic strut on the lid in back?

Yeah that mount will put a notable amount of torque into the area of the clover. Your boxing in below there to cover the header sticking through will help with resisting the load.

A hot glue gun and a couple of cardboard boxes will help you work through the best approach before committing to steel.

 

[lookforjoe]

I thought you had pneumatic strut on the lid in back?

Yeah that mount will put a notable amount of torque into the area of the clover. Your boxing in below there to cover the header sticking through will help with resisting the load.

A hot glue gun and a couple of cardboard boxes will help you work through the best approach before committing to steel.

I still have the factory trunk spring. I never added struts as I didn't want them taking up space in the well access areas, it would need one on each side to prevent twisting the lid.

This is what I worked on for a few hours today

height of header

header protrusion into trunk - only about an inch

made a tie plate ("C" section, 1.5x.5", 1/8") that uses the trunk hinge plates for starters

clearance off that

plate anchors welded

additional anchor point in wall

top plate insert, also "C" section, 1.5x.5", 1/8". Has to be inserted into right side fully, then fed back into left side to a depth of 5". There is another inner wall at that point to prevent further insertion.

3 anchor points on each end

Top plate & trunk plate will be tied together somehow for additional rigidity. Probably a few anchors off a vertical surface added to the mid area of the top plate that do not interfere with the need to push / pull the top plate sideways for install / removal

trunk panel will be formed something like this

I may add an extra bend closer to the top to give a little more clearance where the header protrudes the most. I want at least an inch or so, so I can add the (Volvo/Ford) heat shield panel

This end has the funky cut I have to cap

Top plate will fit over the tie plate with a little work. Besides the need for the trunk seal lip and trunk support, this is mostly just a cosmetic piece at this point. I'm likely just going to bolt it to the tie plate with 3-4 anchors - definitely want 2 in the trunk spring ear area

insert tie plate - notched to clear the trunk hinge on the right so it will fit snug against the trunk wall

I'm going to double the "C" plate to make it boxed for rigidiity - I'll have to notch the lower half the same

put the 4-2 collector back on & checked the bend & cat fitment. Going to use a v-band on the collector to allow me some latitude for vertical cat offset

 

[lookforjoe]

Discussion Thread on Hood pins

Today I got a fair bit done on the bracing - added captive nuts, boxed the horizontal support
welds came out clean on this - forgot to photo before primed

installed that, so I could figure out the center plate

5 M6 sems screws in the plate - the trunk support ties into that, so I need to make sure it's not going anywhere

notch for trunk hinge

came out nice & level with outer panels. I need to figure out a lip seal on the vertical section to keep water out of the trunk. Maybe a flange / lip underneath where it falls within the trunk then thin closed-cell foam.

added back the vertical support for the trunk stay

they have to stay separate since the panels must be independently removeable

where I left off - had to prime & top coat so I'm not looking at all those obvious bolts. I'll paint it properly before I'm done

 

[kmead]

Steel rivets on the trunk spring carrier I hope

Looks great. I agree, getting some distance between the header and the covers is critical, even with the Volvo heat and sound wonder material to come.

Nice job. The feeding in of the beam seems a bit much but hopefully you aren’t taking this apart too many times in the course of the further development of the car

 

[lookforjoe]

Started on the bay access / exhaust cover panel

full cardboard cover

after that, I decided I could just make a box section attached to the earlier access panel I already made - will require some additional pieces added to the upper sides, but this will work - used SS panels I bought back when I did the original bay mod work

 

[kmead]

I like your CAD work.

The box will be smaller than the old FI cooling arrangement that used to be there. Stainless is a good idea from a heat rejection perspective alone with lower conductivity.

 

[Rodger]

Saw this on R&T. Hope your new exhaust keeps you from attracting too much attention. https://www.roadandtrack.com/news/a... -- High Minus Dormant and 90 Day Non Openers

 

[lookforjoe]

Steel rivets on the trunk spring carrier I hope

Looks great. I agree, getting some distance between the header and the covers is critical, even with the Volvo heat and sound wonder material to come.

Nice job. The feeding in of the beam seems a bit much but hopefully you aren’t taking this apart too many times in the course of the further development of the car

That will be welded, I just riveted it to fix location. It's actually only the lower half to act as a 'seat' - the ears are still welded to the top plate. I was thinking about cutting them off & welding to the cross brace instead, but I don't think I need to add the work.

I don't think I would need to remove the cross brace at all for servicing the exhaust, with the manner in which I boxed the C section, the resulting cross section is low enough not to come close to the top of the header, it just gives a nice open access area when removed.

I like your CAD work.

The box will be smaller than the old FI cooling arrangement that used to be there. Stainless is a good idea from a heat rejection perspective alone with lower conductivity.

Thank you. It is a bit of a PITA to manipulate/form compared to mild steel sheet, however the added advantage of not having to paint it is worth it.

Saw this on R&T. Hope your new exhaust keeps you from attracting too much attention. https://www.roadandtrack.com/news/a38114277/new-york-will-now-fine-you-dollar1000-for-a-noisy-aftermarket-exhaust/?source=nl&utm_source=nl_rdt&utm_medium=email&date=110121&utm_campaign=nl25487576&utm_term=AAA -- High Minus Dormant and 90 Day Non Openers

Dang. Don't have to worry about that with the X1/9, however my Volvo has a cut-out for open exhaust above 10lbs of boost

I don't see any mention of motorcycles, which in my area are the greatest offenders in terms of continuous noise levels, and they like to make them rumble, pop & crackle as they ride in town...

 

[lookforjoe]

worked on the cover panel a little

EDIT: Heat Shield discussion -

have to add to the left & right to fill gaps between panels

 

[lookforjoe]

Worked on the 4-2-1 V-band feed into the flex coupler & cat. Took some time to get the pipe angles right so the cat sits parallel to the crossmember. I'm not doing great with my SS welds at the moment. Had some distortion of the flange. Anyway, shouldn't be enough to be a leakage issue, I used lipped V-bands for this.

Should be plenty of room for the muffler exit pipe/resonator to exit down on the left on the outside of the mandrel bend

I can play with the height of the cat to some extent. I think where I have it currently will work, and it should be a cooler setup than the previous

Did some more sketching to figure out how to close off the access panel junctions, and a seal between the two braces.

 

[lookforjoe]

Made the righthand "U" - V bands on either end to allow for maximum adjustment & component replacement - I have almost no clearance off the DP collector. I'd like to pin the VBands after, to make installation more precise, not sure how to successfully achieve that.

Hanger will go here

and here

had to recut the right side of the muffler after this to gain an inch on the left, for the O2 sensor

you can see where the muffler interferes with the O2 bung...

also playing with angle of the muffler - hard to see in the pics. I was able to get it low enough after several manipulations for the heat shield cover I had already made to fit over the muffler & not loose any vertical trunk space

clearance for O2 after cutting the right side of muffler inlet. Another issue is the the Solo Muffler inlet & outlet are NOT parallel to the body - one angles up, the other down. It meant I had to offset the VBand for alignment

I'm happy overall with the way it's coming together

Underside pics - also hard to discern clearance in pics

No room for resonator - tail pipe will also have a VBand at the muffler

 

[Rodger]

I noticed the label on your muffler says Mach25. Just so you know, that is not the one I went with. I wanted quiet so I used their Stealth line, STL25. I am pretty sure their Mach series is more open and louder. You had mentioned that you found the STL25 reference in your post from October 24th, so I assumed that was the one you had ordered.

 

[lookforjoe]

I noticed the label on your muffler says Mach25. Just so you know, that is not the one I went with. I wanted quiet so I used their Stealth line, STL25. I am pretty sure their Mach series is more open and louder. You had mentioned that you found the STL25 reference in your post from October 24th, so I assumed that was the one you had ordered.

Many thanks for noticing that!

That's disturbing - I specifically ordered & paid for the STL25 - I didn't pay any attention to that label possibly being a different model. I did find I had to flare the neck to get the Band to fit snugly, it actually seems to be less than 2.5" - the label says MACH23.

! will have to email them promptly.

 

[Rodger]

I had no issues with the inlet and outlet pipes not being straight on mine, and they fit over my 2.5 inch mandrel bends fine.