Engine/ Turbo question

[91Supra313]

First off Mods, I was not sure where to put this thread so if any of you have a clue after reading please feel free to move to proper area.

My question is about the difference in spool-up times on 7MGTE and 2JZGTE engines. I have been doing some looking around, and I have noticed that alot of the 2JZ motors with turbos larger then the 7Ms, seem to spool up faster.....On the 7MGTE that I had, I was running a T70, with 2.75" IC pipes, and a 3" exhaust, and it didn't start spooling until at least 26-2800 RPMs. Now that I have a 2JZ MK3, it has a 67mm turbo on it and it is starting to spool around 2200. Does that 3mm really make that much of a difference? Or is there some design in the 2JZ motors that gets the exhaust out faster...

Wondering about this because if there will be minimal gain from 70 compared to the 67, then I will just stay with the 67 because of the quick spool......I know I can get a quick spool valve, but I am not paying that kind of money.... I just don't understand why 2 engines that are both 3.0 inline 6s, spool completely differently.

 

[bloodasp90]

if you look at how the heads are built, thats where alot of it plays, cause the valve sizing on a 7m is different then a 2J, thus why it has a different curve. but theres alot that deals with flow and port shape.. ect ect ect.
so yeah, theres alot of differance, but, its not judging on saying one is better then the other.

 

[A. Jay]

I'm sure compression ratio was a factor, in addition to others.

 

[91Supra313]

if you look at how the heads are built, thats where alot of it plays, cause the valve sizing on a 7m is different then a 2J, thus why it has a different curve. but theres alot that deals with flow and port shape.. ect ect ect.
so yeah, theres alot of differance, but, its not judging on saying one is better then the other.

Thanks for the info. I wasn't trying to say one was better then the other. I just couldn't figure out for some dumb reason why it was like that.

 

[bassjunkiens5]

Could be as simple as the turbine housing A/R. Smaller housing equals faster spool.

There's quiet a bit more to it than just that though. Smaller A/R's will allow it to spool faster but "choke" the engine a bit at higher RPMs. Larger A/R's will spool slower but allow you some head room to really wind it up.

Head flow and and valve sizing can help by increasing the volume of exhaust gases flowing through but the velocity will be slightly lower. You want high velocity before the turbo, and volume after the turbo. It gets tricky at that point though.

 

[91Supra313]

Where in TN are you? Wait let me guess.....you're over there near Chattanooga aren't you? Just like damn near every other Supra owner in TN. lol.

 

[bassjunkiens5]

I'm actually about 45 mins from you in Gallatin...

PM me your number if you want. We can meet up and look things over sometime over a beer or two, or ten.

 

[bassjunkiens5]

I'm actually about 45 mins from you in Gallatin...

PM me your number if you want. We can meet up and look things over sometime over a beer or two, or ten.

Actually, I PM'd you awhile back about some part lol. Either way, give me a call if you want.

 

[91Supra313]

got your text and hell I can barely remember to take my meds let alone a PM about a part...lol.