People get really bored at work and researching the nets is better than finding more work.

Exactly

 

What!!! whos going to listen to you ? You need 2000 + post

 

Did someone say something?

 

LOL back on topic

So a Gt37/88 hmm I didnt see that on garretts site is that a hybrid or something not off the shelf ? weres the map also ??

Wouldnt the size of the turbine housing have something to do with PR ???


Looks like the 94 has 4 options

But we can throw all these maps out the window these are corrected GAS turbine flow #s

I know you want diesel maps , if I was looking at a turbo then saw the map and it was based off GAS I wouldnt base my HP and efficiency range on it, I know one big time diesel drag racer doesnt care for maps produced by the manufacture

 

4094 and 4088 share the same turbine, whose map is above. The compressor maps are quite different.

The 3788 packaged for our trucks is theoretically just a 4088 compressor in a 37 frame (smaller turbine) to help spoolup. But if you look at the 3788 comp map in the garrett catalog and compare it to the 4088 comp map, they look quite different, even though they are BOTH 52 trim, 63.5mm inducer wheels.

Is Garrett designing a different compressor wheel just for the CTD application? It's hard to believe, but the map suggests this might be happening. The 4088 map won't go above 3.5PR. But the CTD-specific 3788 map will clear 4:1 PR.

The only problem with this is that the compressor maps for the 3788 aren't like other Garrett maps-- they look like they were drawn by a kid using a marker. Hardly very convincing. No efficiency islands, no rpm lines, nothing. Just a vague silhouette. If that's how these maps are made, then why not make it support 600hp at 5:1 PR with 90% efficiency?

So IF we give these 3788 maps any credibility, then we would have to think that they are different than the regular 4088 maps.

The 3788 isn't an off-the-shelf turbo in the sense that Garrett only sells it packaged for the diesel trucks.

It's hard to believe they would come up with a special wheel for this application, though. The Stg1 and stg 2 CTD turbos appear to be off-the-shelf wheels, so why would the stg 3 be any different?

I personally think it's HIGHLY likely that the th 3788 and 4088 compressors are in fact the same wheel, but I can't account for the difference in maps aside from marketing creativity. It wouldn't be the first time someone in marketing got creative without talking to the engineers.



Anyway, on the turbine side of things, the size of the housing has everything to do with PR. You can tell by the curves that a smaller housing runs at a higher PR as mass flow climbs. For example, at 30lb/min, the smallest housing is already over 1.5PR, while the largest housing is less than 1.25.



Don't throw the maps out the window! The hotside of the turbo is a GAS TURBINE-- the maps are completely relevant.

Using a turbine map, you can calculate how much HP you have to be making to spool the turbo. You can find out what RPM the engine will spool the turbo, given sufficient load. You can calculate how much HP the engine has to make to get the turbo to spool, and how FAR into spoolup it will be.

Don't throw out these curves just because they are simple or because it takes a little math to make them dance. They are the key to the kingdom in terms of spoolup and THAT is perhaps the most important quality to know about a street-bound turbocharger.

JMO,
Justin

 

Bingo-- that's the beauty of capitalism. There are only two parties of interest in free transactions: buyer and seller. If they are both happy, then that's all that matters.

Justin

 

Never ceases to amaze me how much good info there is to be found in some of these threads! Hohn, try an ignore any green eyed little monsters, your thoughts an ideas are greatly appreciated!

 

Hmm..how odd.

The most knowledgeable person in this thread has been banned from the website.

 

Ok I found it I didnt put a R in the search , yeah pretty much 40 , also in the search I see the Dmax croud favor the 40 over the 37 and one made 670 RWHP !!!! (40/88) I wonder how Garrett rates these with HP levels on there site RW or FW ????????

 

Banned?

Strange... I didn't feel a thing.

 

I guess the powers that be didn't see his knowledge as a trump over following the site rules.

 

Justin never claimed to be the most knowledgable person, he starts these threads so he and anyone else that cares to can learn. If people care to input ideas and experience and follow the site rules there is a lot that can be tought and learned from all sides, and much information is put in the light and shared to the benifit of all that care to read and learn.

Personal attacks and criticisims never tought anyone anything, and hurt the credibility of the one hurling them.

 

True, but couldn't you think of it as "corrected" or "effective" A/R vice "actual" A/R.

Jim

 

Who?

Jim

 

I supposed you could guesstimate that clipping would "make it flow as if it was "X" A/R.

But then it's only a guess, unless the wheel has been mapped after clipping. I think only a factory clipped wheel would get this, but who knows if it's clipped before or after.

Justin

PS-- fellas, if it's just the same, we don't need to keep dragging out the hiccup in this thread. The problem's over as far as I can tell, and while I appreciate the defenses, they just prolong the diversion-- let's get back to the topic a bit.

If people want to drag out the soap opera element, then please ignore posts to that effect.