When is a Turbo too Big?

I had an interesting experience tuning a speed 6 recently, and ended up writing a blog about it.

Check it out HERE!

Feel free to discuss in this thread!

 

Great post, and so true. Why build a numbers-chasing dyno queen that feels like a dog 90% of the time on the road and only makes good power for a few thousand rpms? Thanks, but no thanks. My BNR S3 is a BLAST to drive, even at "only" 385/380. I think I could still go up to a GTX3071/76 or EFR7163 and still have a great driving experience, but not for now... stock block.

 

interesting read. very confusing though I have never heard of this happening on a speed.

weren't there people who had used a GT40 before ?

 

I remember Mark from Streetunit had a GT40 but never got the car to make power with it. I don't know of anybody else. This is something that can be tuned around too... However, this wasn't a GT40 turbo. I can see where the confusion comes from though as the turbo (a hybrid of some sort) wasn't exactly too big, it was just not matched well.

 

I've seen lots of stories about surge on Speeds elsewhere. I haven't seen the correlation of grams/second and surge before, though. That's a great, objective way to see what's going on.

 

Yeah Mark was the one i was thinking of, but I figured others had one as well. Mark's car was short lived .....

 

Yeah, he was shooting for the stars before the necessary developments with tuning had been made.

 

Good read, thank you.

Did he have either manifold upgraded?

Was he still on the stock mazda flange or maybe T3?

 

That EFR would be more fun since it'll spool quick

 

He is running a custom exhaust manifold with a tial vband setup. .82 a/r

I remember back when Alpha ran the 7163 on his speed 6. T25 flange and it would hit 20psi by 3500rpm.

 

Isn't this supposed to read 2500 RPM?

 

I just looked up the conversation I had about it the other day with Dustin (PERMtuning). He said

Of course Alpha was rocking the stock block so they may have tamed it down a little to prevent noodle rods.

 

I recall 20 psi being on the table before 3k in the thread. The 7163 spools faster than the 6758 and my 6758 would hit whatever I dialed by 3100.

 

Maybe you are right. I can't remember the details that well. I just remember it spooled fast! Not so fast on our ST though. But peak torque at 4krpm on a 2.0 with a tiny headifold isn't too bad I guess...

 

Well one other thing to keep in mind is that the tune plays a pretty big role in how a turbo spools/responds too. Stuff like vvt, fuel, timing, all changes how much massflow (energy) the hotside wheel sees.

 

The focus has coolant running through the headifold which makes it difficult to keep temps up. I'm sure that has something to do with the slower spool as well.

 

I have a GT3071 hitting 24lbs at 3700 on a built motor. It runs out of air up top before my friends GTX3071 does but I'm still showing 430 WHP in summer heat with 28lbs of boost. Spraying 100% meth with a D14 nozzle for aux fueling and Freektuned. I got a great deal on this turbo used like new, the new price tends to keep people away and choosing the BNR units.

 

yup price is what did it for me as well, not that garrets price was to much but the bnr price was perfect.

 

My S362sx-e (same size as a 6266 and 3582) with a 1.25a/r housing is spooled by 3700 RPM (spring pressure currently). It's not the be all end all of performance but for the $900 brand new that it cost it's a hell of a deal.

 

How are we defining spool? Is spool defined as when the turbo will make spring pressure or when the turbo will make whatever you want to dial? The 6758 will make spring pressure below the threshold RPM of 3100, where it will make 2x spring pressure if I want.

Just curious if I need to update my terminology.