SevenSin

Hello everyone,

Since most of my driving is done during the summer with temperatures from 30ºC to middle 40ºC, I have been using mineral 20W50, however, I just noticed that my friend/mechanic has used in the last maintenance a semi-synthetic oil – HPX 20W50
I am now about to use the Wolf GuardTech 20W50 SL/CF (mineral) without flushing the two oil radiators. Will this cause me any problems?

In regards to replacing a stock pre-cat with a GReddy 80mm downpipe, I might re-use the old gaskets - I haven't seen their current condition - and apply exhaust paste/mass to support the sealing. Thoughts on this? (The gaskets seem hard to find in my country!)

Thank you.

Sgtblue

iTrader: (16)

Your profile lists a 93 FD.....

*There is absolutely no need to "flush" in order to use the differing oils. It will NOT cause any problems. And what TYPE of oil to use is not as important as keeping the change intervals regular and a little more frequent than your piston cars.

*Exhaust energy and temperature is higher on a rotary than a piston engine. I've never used the paste before but doubt it would last very long by itself. Main concern is that it might make its way into the main cat and foul it. Just separate the components carefully and try to keep that gasket intact without bending it. If you can't, then I'd look for a vendor that will ship a new gasket internationally or source one from MAZDA. Compared to the turbo and turbo manifold gaskets, those are among the less expensive ones.

SevenSin

Change done.

For others information - the GReddy 80mm downpipe is "plug and play" to the stock exhaust like the sellers claim but you need a matching gasket from DP to MP or otherwise you get a tiny but noticeable leak.

Mr357

iTrader: (14)

The gaskets that go between the downpipe and midpipe as well as the midpipe and catback are generic and can be replaced very cheaply. You may have to find a different retailer since you're in Portugal, but here's what I bought the last time I had my exhaust out of my car.
The thick metal gasket that goes between the twin turbo manifold and downpipe is a different story. Those are Mazda specific and will be very expensive if you want to replace it. I would recommend reusing that one unless it's in a really bad condition.

SevenSin

Thank you I am based in the UK so I have a decent amount of options to buy from before sending to Portugal.
Both the gaskets were in good condition and we found out that the previous owner did use some paste on top.
The problem I seem to have is that the 75mm gasket layout does not fully seal on top and bottom, would need more surface material. Hopefully a 80mm gasket will do the job.

Sidenote: I'm tempted to remove the cat for something else but then I need to tune due to the back pressure according to some threads. The sound is more lovely now, I hope the temperature gets managed better as well. Last year I had 30C at night, 40Cs at 11am and didn't like the car running with 102C.

SevenSin

Hey everyone,

So yesterday we replaced the gasket with a new one without any luck to fix the leak. The fact that the down pipe is 80mm to the main cat of 75mm doesn't seem to be of a big help. We tried different combinations of old (75mm) + new (80mm) gasket and with only the new one which seemed to lead to a higher leak. The car was not entirely cold but not too hot either, only had to move out of the garage and then I naturally had to turn it on between gasket testing. Unsure of how much influence it would be.
Should I buy another gasket or the same size or smaller?

In the future I might replace the main cat and cat back but not so soon so please do not suggest that as a fix. I will save this mod to when I also change the stock air box intake as it would make less sense to do them at different stages since I will need to pay to be tuned in.

alexdimen

iTrader: (13)

Surface area doesn't really matter. It's all about compressing the gasket. You will need to get a gasket that fits in the area that the two flanges mate. A 75mm gasket against an 80mm flange will not get compression where it needs - at the inner ring that prevents blow out.

I am using the Ticon gaskets from amazon with good success on full 3" (~75mm) piping. Get a similar style gasket, but for 80mm ID pipes.

You could also have bent flanges which will never seal properly no matter what size you order. That will require machining or at the very least "persuasion" with a BFH.

My stock cat had flanges that just would not seal reliably. Went to a Bonez high flow and it hasn't been a problem since.They have great flanges.

Speed of light

iTrader: (8)

What he said ^^. Also carefully check the alignment of the flange surfaces to ensure that they are parallel on both x & y axis---it can look okay in a cursory inspection but still be off enough to allow a leak.

SevenSin

Are there gaskets with a bigger fire ring?
The 80mm one I have has it. I will inspect again tomorrow morning.