How do you read a compressor map?

[4sfed4]

Quote:

Originally posted by DirectConnection Ah... 7psi pressure drop on only 13psi. I assume this was tested at max rpm, too. What would you guesstimate the drop to be if you could maintain 25psi up to 6,500 rpms? 10+?

When I tested it, the 7 psi drop stayed more or less constant from 4000 to 6500+ rpm. But, power stayed more or less constant for that range too (since boost was dropping with rpm and airflow was probably staying more or less the same).

Id hate to even estimate what it would take to keep 25 psi at the intake with a stock cooler. It would certainly take a very big turbo that was happy at very high pressure ratios!

Quote:

Something else to think about.... what would that pressure drop be at 13psi and the same stock cooler, yet with the turbo you have now?

Well, 13 psi with this turbo is alot more power than 13 psi with the old one. Since pressure drop is proportional to airflow (not pressure itself) Id say pressure drop would be greater with a bigger turbo (if you could manage to get that extra air through there).

I wouldnt think the slightly cooler air is really going to make all that mcuh difference. Even a 10% increase in compressor efficiency alone hardly makes any difference in power output.

[4sfed4]

Quote:

Originally posted by DirectConnection Ah... 7psi pressure drop on only 13psi.

Also...keep in mind that was 13 psi intake manifold boost with a 16V car. So, that 7 psi drop would probably be less on an 8V car.

13 psi was about 260 whp when I tested so Id say that is more or less the airflow value that will yield said pressure drop. So, if a non worked over 8V car needs 22 psi boost to make 260 whp, then the pre-IC pressure might be something around 30 psi.

[Stratman]

Just got through reading this!! The hours that went by
Just got a turbo done, but needed this to make a short last minute change.
This is what I have for my 88 Daytona- 2.2 Swirlhead, mildly ported, 3 angle valve job, stock valve size, ported exhaust manifold, 22x6x2.25 intercooler, 2.5" exhaust all the way:

50trim wheel in a T03 well machined housing
2.5" turbonetics swingvalve
stage2 turbine wheel in .43 turbine housing

Looking at street/strip. The .43 with stage2 is what worries me.
The .63 is kinda high $ for me at this point, but looking at getting it for sure, wondering how much difference the .63 will make. Don't mind a little lag either to get the car rolling good.
15 to 25 psi is what I'm shooting for.


Thank you guys very much for this post!!

[Dion Ricketts]

Dang, I agree with Stratman. This is a good, but long, thread.

Sorry I didn't get into this until now. I am always late. But on the other hand it wasn't until a month ago that I started looking at what my 360 (408?) is going to need for a turbo.

About the Hot Rod article. I think it leaves alot to be desired. They left out any calculations for temperature. It the air get hotter (which it will), it will be less dense, which means at the same boost, you wont have as much airflow. In the same way, using 100% VE is a farce. The engine will injest X% of the air you push at it, boosted or not. If you push 500 cfm at 15 psi, it will injest 85% of that (at 85% VE). If you take the boosted cfm injested and divide it by the cid of the motor, of course you will get a +100% VE.

Sorry, I didn't mean to rant, but I think the HR article was written to get people to call Turbonetics and order a turbo, not help them figure it out on their own. The Turbochargers book by Hugh MacInnes mentioned earlier is a much better source.

BTW, I think I have successfuly bought all the parts I need to build a new 60-1 with a 1.00 A/R "P" trim, divided tangental, turbo for $450. $125 for a used turbo off a 6.6 diesel, $76 for a rebuild kit, $150 for a 4" inlet, 2 1/2" outlet .70 A/R compressor housing cut for a 60-1 wheel and $94 for a new 60-1 wheel to fit it. Man I feel cheap. Beats the $600 or more it would have cost me to upgrade the compressor from Performance Techniques.

Sorry Stratman, I don't have any answers for you.

[DakotaKid]

Quote:

Originally posted by Stratman 50trim wheel in a T03 well machined housing 2.5" turbonetics swingvalve stage2 turbine wheel in .43 turbine housing Looking at street/strip. The .43 with stage2 is what worries me. The .63 is kinda high $ for me at this point, but looking at getting it for sure, wondering how much difference the .63 will make. Don't mind a little lag either to get the car rolling good. 15 to 25 psi is what I'm shooting for.

I have T04E Compressor Housing with T04E 50trim Wheel and .63 A/R T3 Turbine Housing with Stage III Wheel in my Shadow.
I recently started driving it on the street and I am liking it. With a little help on the cam timing, it will spool decently on the street.
25 psi is a lot of power on the street!

-Bryan

[4sfed4]

Quote:

Originally posted by TrboVan I have T04E Compressor Housing with T04E 50trim Wheel and .63 A/R T3 Turbine Housing with Stage III Wheel in my Shadow. I recently started driving it on the street and I am liking it. With a little help on the cam timing, it will spool decently on the street. 25 psi is a lot of power on the street! -Bryan

When is boost coming on?

[DakotaKid]

Quote:

Originally posted by 4sfed4 When is boost coming on?

To be honest, I do not know.
It seems about 3000 RPM's but that is just a guess.

I will pay more attention to it the next time I have it out.

Currently have the head off getting a bad valve/seat fixed.
Compression results were not great.
120-120-120-70

[Stratman]

So, here's a querry?
If I have a 50 trim (54mm) wheel in this T03 housing, what compressor map do I need to look at?



More pics on this page

[Koreth]

So after reading this thread in its entirety over the course of a couple days, I have certainly learned alot, and it answered many of the questions I've had but had not yet worked up the courage to ask, for fear of seeming unduly ignorant. After 8 pages of facts, opinions and recountings of expeirences, I've come to the conclusion that the selection of a turbo is a fine balancing act that is dependant mainly on the application. I still do have some questions however. Forgive me if I state the obvious, or ask an obvious question and then answer it with subsequent wonderings; that just the the newbie factor kicking in.

First one, "spooled" is considered to be when the turbocharger is spinning enough to be producing boost in the intake, yes? If so, would then your turbo be considered "spooled" if you are at 0 psi in you intake, (no vacuum or boost, but any more throttle and you will be boosting?)?

That said, what I gather is thus:
Depending on your application (street, race only, blend of the two) you want to select your turbine wheel, turbine housing and compressor and/or compressor housing so that it spools when you need/want it to, and still flows the air you need for your desired power level as efficiently as is practical.

So does that mean you want to select a turbine that isn't so small it would spool instantly if there were no compressor attatched (but cant get the compressor spinning without significant lag), but isn't so huge that it causes significant lag time to get it spooled up (but can sure turn that compressor like it isnt there)? And then when it comes to the turbine housing, I assume you want one small enough that it gets the turbine wheel spinning quickly, but not so small it acts excessivly restrictive and thus puts excessive backpressure in the exhaust, taxing the engine while not under boost. But at the same time, I assume the turbine housing cannot be so big that the exhuast gasses are not forced against the turbine blades hard enough, making the turbine wheel take longer to spool, producing lag. Am I correct here? Am I missing anything?

Now regarding the compressor, I assume you want a compressor (wheel?) thats big enough that you can flow the air you need at the pressure level you desire as efficiently as possible (thus the compressor maps that started this thread, to help select the right compressor) but at the same time is not so big that it taxes the turbine and creats lag because of the increased time needed to get it spooled. Now I assume one could always go smaller on the compressor but then at the risk of it becomming less efficient. Do I have this right? I am guessing, the less efficiently the compressor is operating, the hotter the air at the outlet will be? Or will it be hotter regardless in proportion to the compression ratio? Or both? Meh. I'm confused now , I think to much sometimes. On to compressor housings. Can one mix and match compressor wheels and housings, or is that somehting the vendor of the turbocharger does for you? I genuinely am not sure what kind of effect the compressor housing and wheel have on one another, is it the same or similar to that of the turbine side of the turbocharger? Opposite? Regardless, I am guessing that the combination of wheel and housing in the compressor effects how well it flows how much air at what compression ratios, and this is where the maps come in, to aid in the selection of the right compressor. Thus you get the air you need for your wanted power level as efficiently as you can get it, yes?

Wow, that was long and ramblesome. I guess with questions that long, I still have quite alot to learn still. What I probably really need to do is get a hold of a turbocharger, see it in action, then take it the heck apart so I can see first hand how it works. Hmm, I should probably take apart an old mitsu from a boneyard rather than the new shiny $500 one I'd end up getting for the Shelby Z I'm gonna buy.

[turbovanman]

Wow Stratman, thats some serious turbo, pics do tell a story, the mitsu wheel and GN wheel are so small, lol! Let us know how it works out!

[DakotaKid]

I just thought that some of you may enjoy reading this again!
-Bryan

[Stratman]

LOL, thanks TRBOVAN, I forgot about this thread. Definately a good one to read AFTER the 50trim turbo install!

Quote:

Originally Posted by turbovanman Wow Stratman, thats some serious turbo, pics do tell a story, the mitsu wheel and GN wheel are so small, lol! Let us know how it works out!

Hey turbovanman, I forgot to let you know how it works. Here's a new thread
about the 50trim stage2 turbo in the machined stock compressor housing

[turbovanman]

Thanks for the update, Stratman,

[Chris Faulk]

Quote:

Originally Posted by 4sfed4 Also...keep in mind that was 13 psi intake manifold boost with a 16V car. So, that 7 psi drop would probably be less on an 8V car. 13 psi was about 260 whp when I tested so Id say that is more or less the airflow value that will yield said pressure drop. So, if a non worked over 8V car needs 22 psi boost to make 260 whp, then the pre-IC pressure might be something around 30 psi.

Just to add to this fire again...Larry I traded my intercooler off to a guy with a bone-stock '87 GLHS. I think he's got bigger injectors...fuel pump, and a cal. That's it.

He installed my new intercooler and his car picked up a TON of power and required a bunch more fuel. NO lag or boost drop at all...he even used the tubing I made up.

This very same setup on my car dropped 9psi in the tubing/intercooler.

Attached is a nifty Excel file I worked up a few years ago. Give it a look-see. It assumes a certain VE, which you can change if you like. Use this excel spreadsheet with your compressor maps to figure out where you are.

There are tabs on the bottom to change between 2.2 and 2.5 engines.

Tell me what you guys think!

[Chris Faulk]

Quote:

Originally Posted by turbovanman Wow Stratman, thats some serious turbo, pics do tell a story, the mitsu wheel and GN wheel are so small, lol! Let us know how it works out!

How about my turbo? Likey?!

It's getting an external wastegate setup because I don't wanna fool with internal and the unreliable boost control I've always had.

It's a tight fit I must say. phew