Miata Turbo Forum - Boost cars, acquire cats. - Engine Performance

Dyno Rental Cost

SimBa — Wed, 13 May 2026 16:53:48 GMT

I'm curious what people are paying to rent a chassis dyno. I've been wanting to get my car on one for a while now but I feel like every shop I talk to is asking $300-400 an hour with me doing the tuning. I expected more in the $150-200 range per hour.

Rod choice for high-rev NA6 ITB build

-rX. — Sun, 10 May 2026 21:02:51 GMT

Hello guys

I have a question regarding rod selection for my current build.

I�m in the middle of a fairly serious engine project: a high-revving NA6CE 1.6 with ITBs.
The base engine is the stock 115 hp unit, and I�ve already gathered most of the internal components.

Current build overview:

Block / displacement
- NA6CE 1.6
- 81 mm overbore (approx. 1720 cc)
Bottom end
- ACL Race bearings
- Fluidampr crank damper
- Boundary Stage 1 oil pump
- 1.0 mm head gasket
- Target compression: ~11.3�11.4:1
- Toda 3.5 kg flywheel)
Head / valvetrain
- Toda forged pistons 81mm
- Toda 272� / 10.3 mm lift camshafts
- Toda adjustable cam gears + timing belt
- Supertech +1.0 mm intake & exhaust valves
- Supertech valve guides
- Supertech dual valve springs
- Supertech valve stem seals
- Shim-under-bucket conversion
- Head skimmed 0.55 mm
Induction
- Jenvey individual throttle bodies (ITBs)
RPM target
- ~9000 rpm max

My question:

I�m currently deciding on connecting rods and wanted some input from people who have built similar high-rev NA BP engines.

I�ve been looking at:

Carrillo rods (~432 g) � very light, excellent reputation
Maruha rods (~460 g) � slightly heavier, also well-regarded

My main concern is:

Are Carrillo rods too light for a 9000 rpm NA build like this?
Or is that weight actually ideal given the goal of reducing reciprocating mass?
Would you personally go with something else entirely for this kind of setup?

I understand that lighter is generally better for high RPM response, but I also don�t want to sacrifice long-term reliability or introduce issues with harmonics / fatigue margin.

If anyone has experience with similar builds (especially high-rev NA 1.6�1.8 BP engines revving near 9k), I�d really appreciate your input.

Also, if you have any general comments about the build, feel free to let me know, this is my first big engine project and I�m trying to make sure I�m not missing anything obvious before I assemble it.
Important Note:The car will be used as a weekend car, mainly for spirited driving, with occasional track and drift days.

Because of that, I�m not building a pure race engine, but something fun and responsive that can still handle occasional abuse.

Oiling Gurus Needed

Erat — Fri, 01 May 2026 23:41:00 GMT

So i have a technical question and you all are some of the smartest people i know... Shocking i know, because i hang around a lot of dumb people.

I'm going to do the best i can to explain the situation, with pictures and videos.

I've got this whole new engine setup. We went from dry sump to wet sump. And I'm having oiling issues during the turns.
V8 (LS)engine, sitting the wrong way around. Front of the engine is facing backwards.
I got straight for 10-12 seconds and turn left for about 8-10 seconds. This left hand turn is about 2 lateral g forces.
Oil pan is a custom built that myself and the oil pan builder designed for the application. I put 9 quarts of oil in it, this is about 1/4" below the windage tray. I'm running maxima 50/30 oil.

Now unlike a circle track car, the engine is sitting the proper way around so oil flings off the crank the same direction it sloshes in the turns. They also have really deep (like 8-10 inches) of sump. I don't have that luxury because the crankshaft is basically laying on the bottom of the boat. I'm suck with this flat pan.
I did have them install a makeshift "sump" with trapped doors. Maybe it helps. It also has pretty big "wings", think batwing oil pan from the early LS / corvette C5 days. That's kinda what we were going after with this.

My question is. What would you do to improve oil pressure? Where do you think my problem is? Maybe it is not the oil pan, perhaps it's a capacity issue(too much, too little)? Oil trapped in the head? Too much flow from the pump(Oil pump is Melling M295HV)? Oil weight issue? Breather / crankcase vent issue? Or anything else that i haven't thought of.

I already ordered an accusump, because if i'm not going to have oil pressure i'd at least like to have oil instead of air between the bearings.
I did check pickup depth to the bottom of the pan, but i'm going to check it again because i'm taking the pan off. I'm debating on sending it back to the oil pan builder for modifications, unless there is something i can do myself. One of the biggest issues is, i can't just go test this in the back yard, i basically have zero ability to do any testing and make changes, we only race there is no testing. Last weekend was our one and only test and tune (and i learned a lot). That's one of the biggest challenges, getting it to work properly and quickly. I've watched guys struggle to get their program to even finish a race for almost a decade now!

This is the incident. My vertical marker when i go WOT is when i enter the turn. Oil pressure immediately goes from 80-90psi down to 45psi. It kind of holds half way through the turn and then dives to 25psi where my oil pressure safety is and shuts the engine off.

This is a shot of the oil pan (roughly where the pickup sits) and the direction in which the oil sloshes in the turn. (red arrow)

Also, i have a video tour of the oil pan and i sincerely apologize for the vertical video. I wasn't planning on making this post, but feel free to crucify me.

Ebay RX-8 Yellows poor low duty cycle performance

ptato — Tue, 21 Apr 2026 21:12:42 GMT

Bought some RX-8 Yellows and ending up with strange tuning issues at the low end (idle/overrun). Having to add a lot more fuel to cells near 20-30kpa to keep AFR even; more fuel than cells above them.

Wondering if this is due to incorrect dead times, or if its just a chinese knockoff?

Valve Guide damage / Which valve guides to get

Stoffl — Sun, 19 Apr 2026 05:00:48 GMT

Hi,

Currently rebuilding a crusty VVT engine - see also Build Thread with lots of Pics here https://www.miataturbo.net/build-thr...ebuild-111237/ - and have now been informed by the mechanic that the valve guides should also be replaced when handed over to the machine shop. Lots of play in the valves.
I've attached two short videos to the post.

Now, the destroyed previous NA BP engine rebuilt in 2022/23 had Freccia OE replacement iron aftermarket valve guides. I pulled the destroyed head apart yesterday to inspect the old NA BP valve guides and found some odd scoring in some of the valve guides. Most notably Intake valve 3 & 7.
Also a bit less on some exhaust valves. Lots of marring and ring shaped grooves ?
The intake valves were also pretty damn stuck to the keepers. Valves spring fully compressed and I had to wack the valves from the bottom with a piece of wood and rubber mallet pretty hard to get the valve keepers loose.

Intake Valve 3 from destroyed NA BP Head

Intake Valve 3 from destroyed NA BP Head

Intake Valve 3 from destroyed NA BP Head

Intake Valve 7 from destryoed NA BP Head

Anyone seen valve guide damage like that before ?

Also, for the new VVT valve guides - I'm thinking no iron for the VVT. The only bronze valve guide options with somewhat short term availability in the EU seem to be:

Supertech - 8 x intake, 8 exhaust
GSQ - just sets of 8, no distinction between intake and exhaust ?!?

I'm thinking Supertech ?
Will be running OEM cleaned/reground exhaust valves and new hardened Osvat intake valves, stock springs/keepers.

And for main / crank bearings, the previous destroyed NA BP engine had ACL Race.
Should I get ACL street bearings for the VVT rebuild ? Or stay with the ACL Race ?
Engine only sees a couple track day sessions per year, rest street.

Attached Files

WhatsApp Video 2026-04-16 at 08.53.54.mp4 (572.8 KB)

WhatsApp Video 2026-04-16 at 08.53.54 (1).mp4 (1.75 MB)

Kraken kit

Fast Freddy — Tue, 07 Apr 2026 00:12:29 GMT

My kraken kit arrived today! Question is, am I supposed to use a gasket between the manifold and turbo? My FM kit did not require one. Thanks in advance.

Issue when installing an oem oil heat exchanger on a 1.6.

peteucg — Sat, 04 Apr 2026 14:56:32 GMT

Hi all,

I am in the process of turbocharging my mx5 na 1.6, and I thought it would be a great idea to add a heat exchanger (I live In Greece, but I want the oil to get up to temp faster, during winter).
I bought a used oem that came with the longer stud.

I placed the stud by hand until it couldn't go any further and installed the exchanger.
Placed the nut and just tightened slightly.
The issue is that the threads left on the stud are not enough for the oil filter to even hold in place.
So, either I am doing something really stupid, or I have the wrong stud...

I did some investigation on the net and found out that there are 3 different studs.

short stud for oem without a heat exchanger
BP4W-10-319 (longer; heat exchanger fits on some blocks)
E5B6-10-319C (should be even longer by ~1cm, which would be ok)

I assumed (:confused:) I had the BP4W-10-319, as what was missing was that extra ~1cm.
Made an order to Bofi using the genuine mazda part number E5B6-10-319C, and when it arrived it was the same length......:facepalm:

So, I am at a dead end with this. :violin:
Actually the only alternative I can think of, is to use a the nut of a sandwhich plate instead of the oem, but first I would like to see where I was wrong and how I should do it.

Relevant links I found regarding installation, part numbers, etc...
https://www.miataturbo.net/engine-pe...acement-68867/
https://mazdas247.com/forum/t/dont-u...ce=chatgpt.com
MazdaSpeed oil cooler how-to for FP & FS engines

TL;DR.
After installing oem heat exchanger with stud, there not enough threads....
What can I do now???

Thanks in advance!