Does anyone know the specs of the stock turbo? I know the s4 and s5's have different manifolds but just about everything else is the same. What is the size or A/R of the compressor and the turbine side? I know it's a decent sized turbo compared to stock turbos on other cars, but just how big is it?

I'd like to know this to help me understand how big of a difference there is between the stock and aftermarket turbos, and just to be able to compare our stock turbos to the stock turbos on other cars.

 

is there a page in the FSM which would have this information?

 

Bump. I'm wondering this too + can't find it

 

It's a Hitachi HT-18, but I'm not sure about any specific numbers.

 

I can't remember were I found the info, but it was said the hot side is equal to a .84 T4

 

Old thread. Arghx answered his own question nearly 3 years later, lol.

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/stock-turbo-wheel-size-818137/

Hotside AR is 1.0. I've also confirmed these wheel measurements with a set of calipers.

 

The stock turbine is way to small to be an 1.0 AR

 

If you search, you'll find the concensus is that the S5 turbo has a 1.0 A/R, and the S4 turbo is .84 - 1.0, depending on who you ask. The problem is you have to use calculus to determine the actual area of the turbine inlets, which means calculating the true A/R is above a lot of people. But you can certainly measure height and width to try to get an estimate.

Here, I searched for you:
https://www.rx7club.com/2nd-generation-specific-1986-1992-17/stock-turbo-r-777982/

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/whats-r-stock-s5-turbo-595043/

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/need-some-info-stock-fc-turbo-charger-495691/

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/s5-stock-turbo-specs-267560/

Also, remember that A/R = Area / Radius, so it is a ratio. You can easily have multiple turbine housings that look to be different sizes, but actually have the same A/R.

 

Learn something new everyday. Thanks for the clarification.

 

Thanks a ton. I'm just trying to figure all this turbo stuff out still. This helps a lot. +rep lolz