Niiice

I took my recently blown '93 to Rick's Rotary today for a compression check and I cannot say enough appraisal for him. He was patient and answered my questions.
My compression readings:

Front rotor: 9.0, 9.1, 9.0 (awesome)
Rear rotor: 8.5, 4.1, 3.5 (blown seal)

I've read a lot of threads for 2mm vs. 3mm seals and from what I've heard, 3mm are the way to go. Thy are 50% thicker and will last longer under similar driving conditions as the 2mm. The benefit of the 2mm is that they're designed to fit the housing better for better air flow. However, the 3mm is stronger and more duarble. Rick snapped a broken 2mm seal in front of me, but the 3mm are so good he didn't have a single broken one so he couldn't display the strength of them

I'm sure people will say 2mm are just fine to run, and no doubt they're right. But the 2mm broke on mine so it seems logical to try a 3mm.

To be honest, I have a bad HKS intake on my car. It's smog legal, but it's not cold air intake. It takes air from the engine which is already hot, then heats up my fuel to the point of detonation. So on my expensive list I have to get the cold air intake/box, and I'm getting the Apexi power fc. The GReddy air/fuel meter is looking kind of nice about now too, while I'm at it.

Anyone know of a used power fc for sale?

the_glass_man

iTrader: (2)

Check for the sale forum for a power fc. I wouldn't go with 3 mm, buts thats just me.

particleeffect

well my motor is being built right now, i'm going with 3mm over the new 2 piece 2mm. why not?

BigIslandSevens

iTrader: (4)

it cost about 350 bucks to have your rotors milled to accept the 3mm's. So you think you won't blow an engine with 3mm seals?Hahaha!!! That would be nice!!. The cost of the seals goes up as well. The biggest advantage to 3mm seals is that you have a LITTLE bit more leway with detonation. A GOOD engine builder/tuner SHOULD be able to build you an engine with the same power range with EITHER 2or 3mm seals. Once you go to 3mm seals you have to stay with them unless you buy new rotors!$$$ Either way is OK by me, Whatever your budget allows is the only limiting factor I guess! Good luck!

Rx-7$4$me

SO what was it that blew your motor?

particleeffect

yeh, and it's only costing me 150$ for 3mm.

BigIslandSevens

iTrader: (4)

to get both rotors milled? where at? I've gotten that quote before but it was for each rotor. Thats a good price for both!

particleeffect

maztech in tampa fl. he sends them somewhere though.

Niiice

I got quoted $500 for parts and labor to upgrade my seals during the motor rebuild. Seems steep compared to $150...

The blown motor was caused by my non-cold-air intake. It was sucking in the hot engine air, rather than the cold air from the bottom of the engine. Be sure you get quality, that's all I can say.

TwinTriangles

I always heard that 3mm seals will allow you to safely up the boost allot higher than you could with 2mm...

xstacy7

This is what Pettit Racing told me...

With the 2mm seals they wear the slot out a little bigger. They say when you come back after doing a rebuild to put the seals in the slot...if you go back with 2mm, they tend to have a slight amount of "free space" to wiggle about in there. Well what they do is mill it out to 3mm so they are nice and tight. This is just what i got from them down there...

rynberg

Not true at all. Some of the dedicated drag racers are running well over 20 psi of boost with the stock 2mm seals. That statement would be true with the Hurley 2mm seals which no one uses on boosted rotaries anymore....

Riccardo

iTrader: (1)

Just a question, what was the condition of your rear rotor housing ? Did it need replacing ? were the seals actually blown or were they stuck ?
Thanks

Niiice

I'm not sure yet on the condition, I just took it in for a compression check. He's booked for weeks, he said the heat wave we just had killed a lot of motors. He thinks I broke/chipped mine, since it has the rough idlei but a smooth drive. Other than that, I don't know what else has been damaged or if the housing's okay.

JeffShoots

This is the best reason to go with 3mm seals. If you have the money for NEW rotors stay with the 2mm seals. Used rotors need the 3mm to be tight.

Later, Jeff

Rx-7$4$me

So your telling me HOt intake air blew your motor? There are a ton of people on here that run hot air intakes that have not blown their motors.... what are your other mods?

Niiice

I don't have an upgraded intercooler yet, so I either get a different exhaust or get a bigger and better intercooler. Do the ton of people have non-stock intercoolers?
My current mods:
HKS intake
M2 Downpipe
M2 Exhaust (highly recommended!!)
M2 modified ECU (switching to the Apexi Power FC)

Not that much, but there are a few other minor upgrades.

BigIslandSevens

iTrader: (4)

Sooo... what happens when you blow your 3mm seals? Do the grooves stop expanding for some reason? It makes sense that the grooves would expand but to say that 3mm seals will stop this from happening is a bit of a "stretch"

JeffShoots

No the groove gets warn not streched and it has nothing to do with "blown". It's just the wear in the groove. If the groove was too big for 3mm it's just time for new rotors.

NorthwindHost

I don't know where so don't ask but I read that the 3mm apex seals are overall a better choice because it actually helps the engine last longer.

BigIslandSevens

iTrader: (4)

I was refering to streching,or expanding as the wear . Sorry to confuse. Also i understand that blowing the seals does'nt always affect the groove. It just was sounding like some were thinking this would be a cure-all for the wear problem. I know i'm going to hear it for this but think of going to 3mm seals like oversizing your piston rings(In a piston engine not ours!!)Haha. Eventually you have to rebore. essentially replacing the rotors to us.

hyper7

just an idea but if we were to take a motor with say 50-70k on it and take it apart and look at the 2mm "free play". say we look at it and it has a very small amount of play, mind you the rotor is out and cold. now think of having the same rotor and 2mm seal put in the car. start it up and drive it around. there is a large amount of heat in the engine, could it be possible( for those who are concerned about "free play") that from the heat, the metal of the rotor expands and makes the "free play" of the seal now tight? just thought i would bring it up to either confuse you or make you actually think about if its possible. im not sure it is but... i would like to say that i will be going with 2mm 2 piece seals on my upcoming rebuild that should produce, hopefull (goal) 450rwhp, properly tuned.
just throwing out thoughts!!

SkulkR1

iTrader: (1)

I have heard that the oil injection system will not provide enough oil to properly lube 3mm seals and will cause excessive rotor housing wear for a street car. Would be ok on a race car with lots of premix.

Ceramic apex seals are the best solution but cost lots of $

BicuspiD

This doesn't really seem to make sense - improper intercooler ducting would have more of an effect.

Cold Air intakes on a turbo setup are not as essential (as they are in NA), as you are feeding it into the hot turbine, and compressing it to boot. Warm air in - turbo hot air out.... cold air in - turbo hot air out. I bet that even a 50 degree difference in intake temp at the filter doesnt equal ~5 or 6 degrees of temp difference in charge air at the throttle body. Now N/A applications are a totally different story.

Niiice

I would disagree based on logic and rational. If you compress cold air, it becomes hot. If you compress hot air, it becomes hotter. Very simple. Sure, many people run with non-cold air intakes but how many of those people have stock intercoolers?