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I love my high compression NA build. Most of the fun, with a lot less drama. Been together for 4+ years and my only issues typically parts failing due to age/wear.
So, both manifolds cracked in the same place- right where the cylinder 1 runner meets the flange. I pulled off the new broken manifold and welded up the cracks in both. I laid a pretty heavy bead to try to reinforce this area. Then I checked them both for flatness:
Both manifold flanges warped pretty bad, with the center high and the ends raised 1-2mm. I know Lars flattens them after he welds them up, but my guess is that there are still significant internal stresses in the manifold, and after a few engine heat cycles they warp again. I put one of them on my belt sander to try to flatten it out:
This was after 20 minutes of sanding. I never finished, as my belt sander motor caught on fire; guess it wasn’t made for heavy jobs like this. I dropped both manifolds at the machine shop this morning; I’m going to give this setup one more go, on the theory that the manifold’s internal stresses are now properly annealed after many heat cycles and it hopefully won’t warp again. I realize that this is probably an exercise in futility, but I’m doing it for science.
Last edited by Schroedinger; 06-12-2019 at 03:07 PM.
Mine has cracked again between 2 & 3. Only one place this time. I wonder if part of the problem with welded logs is not doing a root pass and then more passes, but not sure. I know that boiler work requires that. I'm going to make sure I don't need to ob-round my holes. I do have relief cuts.
Seems to me that it is not apples to apples to compare a 200 HP turbo build against a 150 HP N/A. Should be both 150 HP for comparison. IOW, something around 4-5 psi, small turbo, on an otherwise stock engine. Seems to me that it would be considerably more robust.
If Kraken had been around, and I had known about logs cracking, I would have paid the $$ for his TD04 cast manifold. I suppose I might end up there someday anyway.
Lars and I have been communicating and he sent me the 2nd manifold at no charge. I’m a huge MKTurbo fan and he has been great while I problem-solve through my issues. I know he’s also working on a longer term improvement to his kit, but it won’t be available for the 1.6L. It is a budget turbo setup and overall I feel I’ve gotten very good value from it. I know there are other alternatives but I haven’t seen anyone pushing them hard on the track yet, so we don’t really know if they will have the same challenges. We pays our money and we takes our chances.
Seems to me that it is not apples to apples to compare a 200 HP turbo build against a 150 HP N/A. Should be both 150 HP for comparison. IOW, something around 4-5 psi, small turbo, on an otherwise stock engine. Seems to me that it would be considerably more robust.
DNM
I've been thinking more about this comment. I'm doing Track Night In America on June 27th, maybe I'll turn down the boost and see if I fare any better from a reliability/overheating standpoint. It certainly couldn't hurt.
Nice flat surfaced manifolds. Put it all back together today.
Also managed to score a hardtop. It’s in decent shape, and even matches my car.
I dialed the boost down from 14 psi to around 10 psi. That should be about 170-180hp. Track night on Thursday, we’ll see if I can make it through a few sessions without breaking anything.
Last edited by Schroedinger; 06-25-2019 at 10:24 PM.
Track Night In America tonight at Road Atlanta. In the 90's and humid, pretty damned hot.
I'll post a video later, but in short- the car was perfect all night. No more overheating, no more mechanical vibration under the seat, no more cracking manifolds. The hardtop is a magical thing. My best laps tonight were 1:51, a solid two seconds faster than my previous outing when I was running with 30-40 more HP. It's hard to overstate what a difference it made; it really has me thinking about getting a wing and building a splitter/air dam for the front. I finally have the pressures dialed in on the RS-4's, I'm getting closer with the damping adjustment on the Xidas, and the brakes were great.
I'm still tingling, probably more fun than I've ever had on the track. I was in the Advanced group and there were a few S2000's and race-prepped NC's that I ran with; I had no trouble keeping up, actually was faster than some. I was talking to them at the end as they were loading their trailers; they couldn't believe I was just going to drive home.
Hahaha... that would have been amazing. I was basically the same speed as the NC race cars and the S2000's +/- a second or two, with driving being the major variable (as always). A little more tweaking with tire pressures and suspension damping might have got me another second.
The exception would be the Miata Afterworld NC race car, which may have been the fastest car in the whole session. Excellent driver, race slicks, tons of power. I don't know what was under the hood but it was pulling away from me in the straights about as fast as a C5 Z06.
I’ve done three track days at AMP this month. Started towing Rocinante to the track with a tow dolly and my van.
It has been in the 90’s all month, and riding to/from the track in air conditioning is pretty great. It’s also a perfect paddock vehicle, good place to camp out of the sun and heat. The only thing douchier than track stickers all over a Miata is track stickers all over a minivan, so of course I had to do it.
Unfortunately I’m still having overheating issues, even with the Supermiata radiator and running wastegate boost pressure. I think the intercooler taking up the whole bumper mouth is the main issue. I ordered the Singular hood vents, hope they help.
Last edited by Schroedinger; 08-21-2019 at 08:53 PM.
Yes, that is clearly the case and the huge Vibrant 12800 that I have in there is complete overkill for the amount of power that I’m running. The “right” solution would be to get a smaller intercooler and reposition it; however, that would involve buying a new intercooler, removing the bumper, fabricating new mounts, re-doing my charge piping, testing for boost leaks, etc. A lot of work. I’m really only overheating on the hottest days, and late in the sessions. My hope is that by chopping up my hood I can get enough airflow to avoid re-doing all that work.
06-12-2019, 02:17 PM
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