antnicuk

(sorry, just realised this is in the wrong section)

I have a kit car with a turbo II engine in it, i first ran the car with the stock turbo and it went really well, its mildly street ported Series 5 engine running on a microtec ecu. I then changed the turbo to a TO4 E and since then its blown twice.

Has anyone seen a tip break like this before. The engine died on the dyno rollers at 10psi with everything seemingly ok (AF's inj duty, temps etc). It had been worked harder at higher boost while drifting with no problems on the same set up only weeks before. I went back to the rollers to map up to 1 bar but never got that far. It seems a strange way for it to break. There is no housing damage at all (bonus i spose)

The tip was still in situe when i stripped the engine and there is no damage to the rotor.

This is the second time the engine has died since fitting the turbo and manifold, before the turbo change it was driven in anger on track many times without missing a beat. Its only ever running quite low boost. The fuel pump and filter were changed after it went last time and the injectors were flow checked, I also run premix. The tip breakage is very similar to the last time.

Any ideas.?? I have many years experience with rotaries and build my own engines and have never had problems like this before, i also use the same rotary specialist to map on the dyno and they have no idea. The car has all the required supporting mods, runs on colder plugs and 99 ron fuel.

One thought, I have a divided TO4 turbo and my manifold is divided all the way to the turbo so effectively, one port feeds one side of the turbo and the other port feeds the other side of the turbo and they will never meet to balance out. is this a problem? (Its a home made manifold).

classicauto

iTrader: (3)

Are those OEM seals?

To me, the slot clearance is suspect on the second seal break. Any shots of the rotor slots?

Super cool car BTW though

Also, you may want to have a look at your housings in the sprak plug area. Measure the sealing surface across the width of the housing and look for a bulge that has developed around the plug (leading)

antnicuk

i can take a pic of the rotor, are you thinking too slack or too tight? the last time it was the other rotor which doesnt help!

classicauto

iTrader: (3)

I would guess too slack, but for sure have a peek at the housing spark plug area.

For more info on the heart of that issue, check out the thread "why apex seals fail" in the rotary performance section. I have seen used housings that retained their bulge after tear down, if one was reused and the bulge missed during assembly, its very likely to cause a break in the center like that as oppose to the "regular" corner break.

antnicuk

thanks for that, they are mazda seals BTW.

i did check all the seals back to back for warping etc before i fitted them back the 2nd time it blew, the first time they were all new.

Barry Bordes

What heat range spark plug are you running?

Does the exhaust port have a nice bevel?

What AR turbine housing?

Nice looking package!

Barry

patman

iTrader: (3)

what does the seal groove in the rotor look like?

that is a sweet car by the way, what kind of kit is it?

antnicuk

Hi
Thanks guys, the car is called a Stylus, it was designed by jeremy phillips who built Sylva's and Fisher fury. low volume English Kit cars

The grove in question is fine and the rotor has no damage, new or old. I will measure the clearance when i put it back together.

I'm running 10's and 11's spark plugs.

The turbo is a TO4E with a 1.0 a/r on the exhaust side.

antnicuk

Pic of the the rotor housings and the apex seal grove in question

K-Tune

iTrader: (26)

can you take a picture of your exhaust ports? are they stock or have they been reworked?

antnicuk

the exhaust ports are enlarged, i machined the stock lip away all the way around and then put another lip back in,

bad 83

iTrader: (3)

The only time I have ever seen apex seals break like that is either from over boosting, or running high compression rotors with a bad tune and detonation. BTW, looking at those sparkplugs, just a suggestion, stay away from the Autolites.

antnicuk

the engine is stock turbo II componants, as for tune, i was in the hands of the tuner but they are a specialist Rotary tuner (ReWorx) who i have used all the time.

There is mention of an ignition issue, the Microtech is well thought of in england and i have heard stories of the timing doing strange things, makes me wonder if that maybe something to do with it

bad 83

iTrader: (3)

The comment about the Autolite single prong plugs, I would take to heart. There is a reason Mazda designed the spark plugs the way they did. I have seen those single prong plugs burn the tip off and go into the rotor housing and destroy apex seals in a similar fashion.

Tyler [S5 FC]

Wow, that car looks so fun!

Barry Bordes

Antnicuk, can you show us a picture of the exhaust port "as run" after the failure?

After porting I use a small diamond file to chamfer the chromed liner followed by 400 grit abrasive paper.

All port edges need a final rub test with your finger, but especially the closing edges. As Lynn Hanover says " Imagine your tongue sliding over it at 100 mph."



Barry

stevensimon

iTrader: (11)

if your apex slots are within tolerance then im going to go with detonation. im assuming your apex seal springs are new? i had problems breaking apex seals with a similar pattern to yours and it was always found to be either spark misfire or detonation. just one little ping can blow the stock apex seals to pieces. you should try out the rotary aviation seals for your next build. they claim that they will not crack or break and are at a very similar price point. after i switched to them, i have yet to blow another motor.

also you should think about modifying your mani a little bit. one rotor will always make more power than the other, could cause for some funky turbo turbulance which may or may not be a contributing factor in this. i would go with a more semi divided setup but i also dont know an thing about home built manifolds.