Car makes noticably less power after Autobahn incident (intercooler pipe came loose)
 

First things first. About a month ago I was cruising on the Autobahn. 5 miles into Germany I did some pulls close to 150mph to check the top speed. (which went bloody hell great btw.) I decided it was enough and cruised a bit at 125mph for another 2 miles or so. Wanted to overtake a car, went in boost a bit and.... WOOSH, PPUPHHHH... no performance... pulled the car over to the side and stopped, car died because it couldn't keep an idle. (In total I was still less than 10 miles into Germany so the fun was short.)

After the first moment of 'omg what just happened? did I blow my engine?!' I realised the engine and internals weren't blown and it was probably something else. Stupid thing was I couldn't find a pipe/hose loose at the turbo/intercooler or anything, neither did the German ADAC guy with the enormous beer-belly.

After waiting for more than two hours we finally got on top of a flatbed towtruck and drove to the nearest Mazda dealership. (ADAC thought they would know the car.) Well of course they didn't understand a lot because of all the mods, but luckily I finally spotted the problem. (why I did spot it this time I do not know) The pipe that goes into the air outlet at the turbo was completely loose. (I could stick my finger between the gap) With my current but old FM II kit this is a metal pipe.

So I fixed that easily and the car started just fine. AFR also fine, etc. I went home and staid in vacuum all the way, still quite scared and I didn't want to stress the car before I talked to some people with more skills and know-how.

Together with a good friend of mine (and driver of a 300+ whp miata) we fully checked the car. I noticed that it had less performance and that the old Bosch BPV sounded different. We took every pipe and hose apart and installed everything properly again. Also installed a 'new' BPV (the bigger, old FM unit) The thing is, the car drives great. revs happily, starts easily, nothing to worry about, solid AFR's, etc. BUT like with the old BPV after the incident, performance is noticeably worse.

It looks like I'm making at least a psi or so less boost, but more noticeably it feels like I'm spooling up A LOT later and slower. Feels like I'm missing 30 horses if it ain't more. The wastegate actuator was a bit loose but after fixing that still no difference. I'm also hearing a very faint high pitched 'shhhhh' sound when accelerating. Only audible at speeds less than 20mph though. I guess it's probably a slight vacuum leak? (But man, that could never cause this, right? Idle is fine...)

Any ideas what to check/do?
Thanks guys! :owned:

PS
I'm running a 1998 NB, Old FM II turbo kit so with the Link piggyback ECU and 4 extra injectors placed in the intake manifold. FM 2.5" exhaust system, happy meal clutch/flywheel kit.
NGK sparkplugs, 8.5mm leads, new oils all around, new K&N filter.
Car dyno tuned last year or so, 246hp on the engine, 300nm (220ft lb)

What ECU are you using? Sounds like a stock ECU and a MAF?

Ah, yeah some more details would probably be smart...

1998 NB, Old FM II turbo kit so with the Link piggyback ECU and 4 extra injectors placed in the intake manifold. FM 2.5" exhaust system, happy meal clutch/flywheel kit.
NGK sparkplugs, 8.5mm leads, new oils all around, new K&N filter.
Car dyno tuned last year or so, 246hp on the engine, 300nm (220ft lb)

(slightly old picture)

https://www.miataturbo.net/attachmen...ine=1347904986

I can't help with that ECU - it would be nice if you had something a little more common, so the forum collective could help.

Yeah absolutely. Too bad there isn't a dyno station nearby that doesn't charge $200 for a single run... A dyno plot with power/afr would also be handy to have.

I've blown couplers plenty of times... unless you kept trying to boost, there should be no adverse effects.

Nope I immediately lifted throttle and did not try to do anything other than rolling to a stop on the side of the autobahn. It stalled immediately which isn't extremely good for the turbo and stuff, but I don't think it can cause my symptoms.

I'm not a tech kinda guy so at first I didn't knew what just happened so I was extremely careful, lol.

It's strange because the car drives absolutely fine... Darn it, I might just need to do a dyno to see if it's not all in my head. :facepalm:

Did you manually spin the compressor wheel? check shaft play?

Everything feels normal, nothing out of the ordinary.
Also checked all my link piggyback ECU settings, still intact.

Any ideas guys? It feels like I'm missing around 30-40hp (yes, a lot) and it looks like I'm doing around 1-2psi less.

Idle is fine btw.

Did you hook up a boost leak tester and try that? You could just have a leak somewhere. Or what are you using for a boost controller? Could you have hit it while you were re-installing everything, and it just needs to be re-adjusted back to your target boost?

Not tests yet, I'll try to find a boost leak tester locally or I'll try to make one myself.
About the boost controller, ouch... I actually can't remember exactly what I have, it's on the tip of my tongue... Anyway, cou can see it here, to the right next to the air filter: http://img.photobucket.com/albums/v4...ject/groot.jpg

We definitely haven't hit that. :)

Check out every single coupler, take it apart, clean the surfaces to ensure theres no oil and tighten it up again. Also disconnect the blow off valve from the intake manifold and plug the hole and do a run. Yes you'll get surge in the process but see if hear the high pitched noise again.

The turbo spins freely by hand, yes? Do you have a CAT in your exhaust? A ~150mph pull at your (previous) power level produces a LOT of heat for a lot of time. Unless you have some special aero work, that last 10mph takes quite a while. Make sure your troubleshooting include things that might have melted in addition to what might have popped loose.

Thanks, I'll write all suggestions down since I don't have a lot of time at the moment.

Turbo spins freely, yes. \i do have a cat in there, just a year old, metallic core high flow thing from Flyin' Miata. Do note that the incident happed just 7,5 miles after the German border... The time that I really pushed it wasn't long. But you are right, it produces a LOT of heat. I'll take this in consideration with my search as well, thanks!

I have two friends with FMII cars that mysteriously lost power. Both causes: Disintegrated CATS. These cars live 3,500 miles apart, the owners don't know each other and the CATS were purchased and failed over a year apart. I saw one of the slags in person. It blew to pieces and melted in place - one giant lump of crap that had a fast car putting down ~155whp on the dyno.

If you don't find any of the simple things discussed already, I would pull the down pipe and take a peek. If it looks like the one I saw, bang it out of there and see if you can hit 160 on the way out of town! :fael:

Wow, that cat has now really cat, err caught my attention! Really do hope that's still in good condition as I need to pass the emissions test here in the Netherlands in less than a month. (I failed last year because of my old cat)

Hopefully not but talking to two different 'miata' buddies in the last month (one local and I saw it with my own eyes), both had failed FM cats that produced symptoms just like you are describing. If it turns out to be the problem, you're best best is to find a performance shop there and have them weld a new equivalent one in. Hopefully there are no bogus BS rules about non-OEM parts and other such crap. :hustler: Good luck with everything!

If the cat melted to a lump shouldn't there be a noticeable change in exhaust note?

You should also have a red hot cat.

Have you checked the turbo to manifold studs? I wouldn't be surprised if one 150mph run stretched them. That or even the downpipe.

https://www.miataturbo.net/attachmen...ine=1348747836

at idle.

I saw that you have the EBC, presumably controlled by the link as intended. If so, it should reach target boost. In my experience the link does a decent job of controlling boost.
If you can't reach boost with a decent EBC, then your turbo is choking on something -> the cat hopefully. It could also be blowing air somewhere else and not into the intake. But since the link uses the stock ECU and MAF when not boosting, and for part of the fuel delivery when boosting, it should also have bad AFRs which you are not reporting. So I doubt it's an air leak.

Extended Autobahn high-speed runs could also cause really hot combustion chambers and from that valve-failure. I hope that's not it, but if it's not the cat you may want to pull the head.

I have build the car together with Jasper. After his unfortunate run in Germany, I have helped him re-installing the couplers that were badly installed in the shop they took him to. We did not boost test the setup, looked at the couplers and they seemed ok. I also checked the torque on the manifold bolts and the down pipe, all tight. No visible cracks.

The cat was on my list of suspects too but since the car sounded not louder or muffled, I guessed it would be Oke. Think we have to check it just to rule it out.

Scott that is one scary picture!

that happened after I blew a motor and the cat got dowsed in oil...that was after trying to run the new motor and it just wasn't quite running well :)

Check the studs!!!!

studs are okay

yeah they are! wooo woooooooo

:makeout:

LOL , thats why I called them bolts in the first post

There wasn't enough change at idle on the car I heard for us to figure it out right away. I never drove/rode in it and on the track I had my own exhaust to listen to. Turbos are already muffled by nature so the exact same failure NA would certainly sound different.

It should be easy to unbolt the cat and look inside to check it's health.


If it looks fine, you could still have a boost leak. Also, check the wastegate actuator preload. If it was loose, it may not be putting the same amount of force on the flapper as it used to, meaning you might have lost your 1-2psi there. You could also have spike really lean and detonated really hard when the coupler popped off. If you haven't replaced the plugs and tossed the old ones yet, pull them out and check for detonation residue (tiny balls of aluminum on the insulator).

We checked the plugs, nothing that indicated detonation, new plugs are installed.
Haven't checked the preload on the actuator yet, it goes on the check list.

Wow, lots of replies! My notification system didn't work any more....
Henk is right, we've got to check everything step by step.

We're both quite busy so it'll take a while. ;-)

Pop the pipe going to the cat off and run it. It will be loud but if it works like normal its sledge hammer and jack handle time.

This Saturday i'll try to pop the midpipe out. My cat is clamped in between two pieces of exhaust (midpipe) with exhaust clamps... And I do not really want to take those clamps off. (We had a bit of trouble sealing them up)

So I'll probably remove everything after the downpipe... so the full midpipe+cat and possibly together with the muffler.

Took off the exhaust this weekend, right after the downpipe and flex piece.
Serious amount of noise that made us giggle like little girls. :giggle: Had a good time, lol...

Took it for a short spin while my friend was recording everything with his phone.

The cat looked better than I hoped, no big blobs or molten stuff, but it looks to be a bit off to the side and it also kinda looks like it's a bit clogged...

But like I said, we took it for a spin and although I think I had more power, it still wasn't nearly as good as it was before... So it can't be just the cat that's causing problems.

metal core?

Yeah, bought last year @ Flyin' Miata. You can't see daylight through the cat because there's a bended pipe after/in front of the cat.

Have you run a compression test yet? That would tell you what shape your valves and/or rings are in...