well thats no help at all. so lets see some confirmed a/r numbers and a trim size.
The turbo I have is an RHC6 which is in the IHI GM1-8 family found on early to late 90’s model GM diesel pickups. I have the GM-3 from the 92-93’s. I don’t have the exact specs as I haven’t taken it apart to measure but here’s some info I found on this family of turbines. The images were no longer hosted but the info is still good.
""I figured I’d bring this up since there is/was some confusion as to what the Borg Warner IHI RHC6 GM1-8 compares to when comparing any of them to a Garrett TO4B or TO4E.
The IHI RHC6 GM8 measures 2.756" major diameter and 1.968" minor diameter on the compressor wheel. There are NO minor diameters of TO4E that measure 1.968". The closest you would get would be the TO4E 40 trim which measures 1.870"…BUT…the major diameter is 2.950". A difference of a finger nail on each side…quite a difference in percentage and overall flow potential.
Now moving on to what is closest- The TO4B S which measures 2.750" major and 1.904" minor.
Here is the TO4B S which has a max choke flow of 37 lbs/min or roughly 17.7 m³/min which equates to roughly 625 CFM. Take the rules of 150 CFM per 100 hp and you’ll see that the TO4B S is capable of enough flow for 300~500+ hp.
Now onto more facts courtesy of IHI. The closest current compressor map that you’ll find is located here:
But this is for the latest series of IHI turbos which aren’t ancient and weren’t made in the 90’s. The updated (ie current) version of the RHC6 family is the RHE61 which is the same frame, same size, same everything except 2000’ish rather than 90’ish.
Note that the airflow rate for the RHE61 is 3.3 m³/min - 17.7m³/min or 116.5- 618 CFM. Now that we’ve gotten that taken care of, we’ll move onto the actual flow maps. Here is the entire updated family of IHI turbos:
Note that the RHE61 barely passes the 20m³/min mark and that spooling the turbo that fast would be the equivalent of trying to boost a VJ11 to 30 psi. As said, the choke flow is 17.5 m³/min.
What does this all mean? Why and I posting pictures of turbos that aren’t the turbo in question? Glad you asked.
Here is the archaic RHB3-RHC9 compressor maps:
The RHC6 family tops out at 17.5 m³/min or 620 CFM.
As far as the turbine, the GM8 measures 2.420" major and 2.030" minor. GM3 appears to be somewhat larger on both the compressor and minor turbine wheel. GM3 measures 2.150" minor on the turbine wheel.
The measurement for the GM8 would be closest to a Garrett Stage 1 turbine which measures 2.319" major 1.918" minor.
Measurements for Garrett turbines are as follows:
Stage 1- 2.319" major, 1.918" minor
Stage 2- 2.559" major, 2.122" minor
Stage 3- 2.559" major, 2.229" minor
Stage 5- 2.798" major, 2.439" minor
N- 2.922" major, 2.071" minor
O- 2.922" major, 2.296" minor
P- 2.922" major, 2.544" minor
Q- 3.111" major, 2.693" minor
much better. not too bad of a cfm flow rate. got any compressor maps? i’m sure many don’t understand what u posted but i appreciate it
lol…good luck finding a compressor map. I’ve searched and searched. I haven’t heard of many running this setup. Hopefullly this thread will inspire more to do so. IHI makes good turbines, and this 15 year old one proves that!!