I'm looking at compressor maps and with the formula i'm using it looks like with an h22 at 8 psi idles under the surge limit. This is a T3 "60" trim i'm looking at.


and the table

RPM
2000 3000 4000 5000 6000 7000 8000

CORRECTED MASS FLOW(CMF)
6.76259617 10.14389426 13.52519234 16.90649043 20.28778851 23.6690866 27.05038468

PRESSURE RATIO(PR) 1.646258503
Is it ok for idle up to around 2k rpm to be under the surge limit?

 

anyone???

 

you will not start seeing a increase in pressure ratio until at least 2500rpms

the turbo cannot surge unless it is making pressure

you want to run like 6-7psi? you will be looking at surge around 14psi assuming it can build full boost by 3000 rpms

 

Depending on which exhaust housing you pick, you won't even have boost until 2800rpms or later. I wouldn't really go smaller turbo because of this as the boost bug can really bite you in the rear when at a race track, and race gas becoming easily attainable.

I guess I don't know which engine its going on, but if you go with the larger housing (.63) you probably won't see boost until upper 3000's and maybe even low 4's.

I run a .48 housing and barely have full boost by 3000rpms, so being close to the surge that low isn't even applicable. Of course I'm not running a Honda, so my info may not work for you, but any help is something I guess.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by turbo_smallblockchevy &raquo;</TD></TR><TR><TD CLASS="quote">
the turbo cannot surge unless it is making pressure. You want to run like 6-7psi? you will be looking at surge around 14psi assuming it can build full boost by 3000 rpms
</TD></TR></TABLE>

Maximum Boost Glossary pg 235 definition of Compressor Surge:

definition #1-compressor surge is when the throttle slams shut and the turbo is still boosting yada-yada-yada, we all know this one.

definition #2-compressor surge can also occur under boost if too much pressure is present with low airflow through the system. The chirping sound heard from the turbo when lifting off the throttle results from this oscillating air volume. This noise is uppressed by the bypass valve. The noise from this type of surge has been described as a "snakelike" sound or a "che-che-che" sound.

The surge limit on the left portion of compressor maps is the area where you get compressor surge. You are boosting but there's not enough airflow, so the air oscillates and makes noise. So you dont necessarily have to be making a lot of boost to cause surge.

 

according to the flow ratings I posted which I got from stealthmodeperformance.com(hmt) putting in my displacement which was an h22 running 8psi.

this is what I get..

I shows I'm on the surge limit up till about 2300rpm. How do you determine when you reach full boost?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by darkspector &raquo;</TD></TR><TR><TD CLASS="quote">according to the flow ratings I posted which I got from stealthmodeperformance.com(hmt) putting in my displacement which was an h22 running 8psi.

I shows I'm on the surge limit up till about 2300rpm. How do you determine when you reach full boost? </TD></TR></TABLE>

I'm willing to bet you calculated your flow rates incorrectly. I used to own a Prelude, and back when I was trying to turbo it I did the actualy calculations and plotted out my numbers on compressor maps. I even went and found out the H22's actualy VE percentage, and I tried to find some way to change CFM into LB/MIN which is the flowrate that most compresor maps are in (Garrett and Turbonetics for example).

Here are the numbers I came up with:

(CID x RPM x 0.5 x VE%) / 1728 = CFM no boost
CFM no boost x pressure ratio = CFM with boost
(14.7 + PSI) / 14.7 = pressure ratio
0.070318 x CFM = LB/MIN (this is the only one I'm not 100% sure of)


(134.2 x 2000 x 0.5 x 0.40) / 1728 = 31 CFM at 2000 RPM
(14.7 + 5) / 14.7 = 1.35 pressure ratio
31 x 1.35 = 42 CFM at 5 PSI at 2000 RPM
0.070318 x 42 = 3 LB/MIN at 5 PSI at 2000 RPM

So even if your turbo was able to build up 5 PSI of boost at 2000 RPM's your airflow would stll be pretty low. An H22 has a peak VE% of 102% at 7000 RPMs. I can give you a very credible source for that number, it came from an SAE study done by a few Honda engineers. So an H22 has a peak VE of 102% at 7000 RPM (peak HP RPM). I used 40% VE for 2000 RPMs, but that was probably a very high estimate. So the actual airflow might even be lower then what my calculations are. But even with a high VE estimate, a high PSI example you can see how low your airflow rate is. You night still be in the surge limit but there's no way of getting around it. That's how it is going to be for any B16, B18C, or H22 with a big turbo and really low RPMs.

 

http://www.stealthmodeperforma...1.xls

this is the table I found... i'm not really sure how to read those numbers. Would you be able to input the right numbers for me? Sorry if that's asking too much. I appreciate the help.

 

Sorry I dont have the program to open .XLS files on my computer.

 

DOH!! well this is the graph copy and pasted.

INPUT
BOOST(PSI) 14.7
DISPLACEMENT(cc) 1834
INTAKE TEMP. 130
VOLUMETRIC EFFICIENCY 0.9
COMP. INTAKE TEMP. 545
COMP. INTAKE PRESS. 13.95
IC PRESSURE DROP(PSI) 1.5
OUTPUT
RPM 2000 3000 4000 5000 6000 7000 8000 9000
CORRECTED MASS FLOW(CMF) 7.447047324 11.17057099 14.89409465 18.61761831 22.34114197 26.06466563 29.78818929 33.51171296
PRESSURE RATIO(PR) 2.102040816
DISPLACEMENT(Cu.In.) 111.9174658
INTAKE AIR DENSITY(Di) 7.79089E-05
MASS FLOW RATE(Mf) 7.847426212 11.77113932 15.69485242 19.61856553 23.54227864 27.46599174 31.38970485 35.31341795

 

Ok from reading those numbers here is what I see:

-When you input the PSI as 14.7, it's probably calculating the flow rate at 14.7 PSI for all your RPM points. You might have to change the PSI to match each individual RPM. EXAMPLE change the PSI to 5 PSI cause we'll assume that the turbo we are looking at will reach 5 PSI at 2K RPM. Look athe flow rates for 2K RPM and ignore the rest. Now redo it but now use 8 PSI because we'll assume that our turbo will reach 8 PSI by 5000 RPMs. Now when it calculates the flow rates, only look at the one for 5000 RPM and ignore the rest.

-The volumetric effiency looks like it might be off too. When you are doing the steps in the above paragraph remember to change the VE to match the RPM. Your average VTEC motor has 100-110% VE at peak horsepower RPM. So for a GSR at peak HP RPM (not redline) use 106%. For an H22 Prelude use 102% at 7000 RPMs. Then below VTEC just lower it to 40-60% And from VTEC to peak HP RPM use 90-110%. The closer you get to the peak HP RPM the higher the VE will get.

-Did you do the calculations for a B18C or H22? I see that the displacement is 1.8L and 111 cubic inches displacement. A lude is of course 2.2L which is 134.2 (L x 61 = CID).

 

BTW, were you trying to turbo a GSR or H22 motor? remember all this stuff is just theory. With a T3 60 trim on a GSR or H22 you'll spool very fast, and you really wont have a lot of low boost low flow surge to worry about.

 

Change the VE changes things around a little bit. It shows at 7000rpm 1.02 VE it shows CMF of 27 it's shows low efficiency.

6k rpm 1VE 22.54 cfm
5k rpm .9VE 16.90 cfm
4k rpm .7VE 10.00 cfm

so it looks like this turbo will spool quick it seems a bit small for the application and would drop boost towards redline... and i'm planning on doing autoX where you would want to stay up there and depending on the track you just might. whats the next size up from this turbo that would seem decent?

actually it seems that with the CID I believe I put it in there right... this is just a bad turbo to choose. I'm having a hard time finding a good one. Did you ever a good turbo for your prelude?

 

I was going to run a T3/T04E .63 ar/60 trim, but when I bought a used kit I ended up getting a T3/T04B 0.48ar/???trim. I was trying for pwer over response. I ended up selling all my Lude turbo stuff before I got around to installing it. My new turbo project is my CRX with B18C and Revhard kit running the same trim turbo. BTW about the CID I just wasn't sure if you were using a B18C or an H22. I thought I read that you were gonna be running an H22 at 8 PSI.

a B18a/b/c is 109.8 CID
a H22 is 134.2 CID

Cubic Inches Displacement = 61 x Liters

 

yeah i was going for a t3/t4 60 trim... but I couldn't find a map for a t3/t4 just the t3 not sure about that... but the 60trim looks decent. I wanted a quick spool because I plan on autocrossing and want that power quick. Although 2-3000rpm for an h22 is pretty damn quick through 1st and 2nd gear. At the same time... as someone I know says "lag for traction, boost for action!" I've been trying to find the difference between t04e/b is it just the size of the houseing? Thanks for all the help.. i'm learning a lot!

 

A T4B will spool slightly faster then the T4E.Physically it is a little smaller and there is a difference in the blade count. Check out http://www.turbocharged.com and look around for the compresor maps.

http://64.225.76.178/main.htm &lt;---that's the link to turbocharged.com

 

i was looking at the 50 and 54 trim t04e and the maps looked decent. how do I dertermine how long it will take to reach full boost. so I can pick which one is better. And do you think I can get either of those trims in a t04b housing? or wold that change the map completely. And these are t3/t4 right?

 

I think I read that boost pattern is determined mostly by your turbine side. The compressor has a little effect on what your boost pattern will be, but it's mostly the turbine a/r that either spools you up fast or slow. Other things like BB or non BB will obviously have some play on your pattern too. The best thing to do is ask around and see what kind of boost people are getting at xxxx RPMs.