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Discussion Starter #1 (Edited)
I've been a long time reader of this mr2 board as I find there are many great discussions and information on here. I haven't posted as I don't own a mkII mr2, but I am often working on a friends mkII mr2, in fact it's in pieces in my garage right now getting work done to it.

I'm having problems selecting a turbo for my needs, I have run lots of numbers but end up going off the right side of the compressor map (choke side) at high rpms on turbos that "should" be a good match for my engine. I know the 3sgte can be built to handle high rpm and some here have it so I'm hoping you can help me. I've raised many turbo question on my board and the answers are just scary, with people thinking it's ok to run stock 330 cc injectors on engines turbo charged up to 250'ish whp (290'ish crank hp) and not touching the stock returnless fuel system at all, while running a piggy back greddy emanage on the stock ecu. They obviously don't know what they are talking about and are buying turbo kit's blindly without investigating them.

I'm trying this board because I figure the 3sgte would be the closest matched engine to the 2zzge in the toyota family when it comes to turbo's, and also this board has a good reputation with very knowledgeable and experienced people.

I want to turbochage my toyota 2zzge engine (the latest in the ge line of engine designed by yamaha, 4age, 3sgte, 2zzge). The engine is a 1.8L with variable valve timing and variable valve lift. It's an all aluminum block and head with mmc (metal matrix composite) coating on the cylinder walls instead of sleeves. Stock fuel cut is at 8300 rpm but I'm currently running the engine upto 9500 rpm. I run a Apexi Power FC ecu (completely replaces the stock ecu) and have full control of the entire engine with the ECU including control of the variable valve timing and variable valve lift.

Here are some specs on the engine itself as I know you probably won't be familiar with it. I've included some of the 3sgte specs for an easy comparison.

3sgte = 86mm bore and 86mm stroke = 2.0 L
2zzge = 82mm bore and 85 mm stroke = 1.8 L

And to answer the question that some many people ask when they see these numbers, no you can't bore out the cylinders to make it a 2L engine. The bore to bore wall thickness is 5.5mm, so there isn't anything significant there to bore.

Camshaft Specs (dual cam profile's, low rpm and high rpm)

Low RPM
Exhaust 7.6mm Lift @ 228 duration (34 BBDC open and 14 ATDC close)
Intake 7.6mm Lift @ 228 duration (-10 BTDC (10 ATDC) open and 58 ABDC close Adjustable To 33 BTDC open and 15 ABDC close)

High RPM (adjustable engagement, n/a typically around 6000 rpm)
Exhaust 10.0mm Lift @ 276 duration (56 BBDC open and 40 ATDC close)
Intake 11.2mm Lift @ 292 duration (15 BTDC open and 97 ABDC close Adjustable To 58 BTDC open and 54 ABDC close)

**The intake came has 43 degrees of adjustment

Valve Specs;
Intake Valve = 34mm
Exhaust Valve = 29mm

Low RPM valve overlap is adjustable from 4 degrees to 47 degrees
High RPM valve overlap is adjustable from 55 degrees to 98 degrees

Inlet Valve Speed of Sound (MACH) Index
the inlet valve mach index is 0.448 @ 11.2mm lift and 9500 rpm

Compression Ratio;
3sgte = 8.8:1
2zzge = 11.5:1

Effective compression ratio @ 8.8:1 and 15 psi = 17.78
Effective compression ratio @ 11.5:1 and 8 psi = 17.76


3sgte rod to stroke ratio (86mm stroke, 138mm rods) = 1.6
2zz rod to stroke ratio(85mm stroke, 137.9mm rods) = 1.62


I've balanced and blueprinted the entire engine, and have the follow upgrades to it;

Darton Sleeves
Crower Rods
Wiseco Pistons
Upgraded valve Springs
Mild port & polish on the head and intake manifold
Billet Steel Oil pump
Baffled Oil Pan
Oil cooler
Fidanza Aluminum Flywheel
IS Plasma Coils
540cc injectors
SF Fuel Rail (with return fuel line)
Upgraded Fuel pump
Aftermarket pressure regulator
Apexi Power FC
Wideband O2 Sensor

The pistons I'm running are at 11.5:1 compression (which is the same as stock). I want to stay with the stock compression because it really helps the low/mid end torque and I'm not looking for large psi or huge hp numbers. I want to run 6 psi on low boost and 8psi on high boost with a priority on quick spool up and run the engine out to 9500 rpm. The couple turbo kits that are out right now run the stock 8300 rpm fuel cut and produce 245 to 265 whp running on stock internals and stock 11.5:1 compression ratio while running 6 to 8 psi. 250+ wheel hp is really all that I want, but I want to be able to run the car out to 9500 rpm as I like to do autox and a longer rpm range is very useful on a autox course.

I also plan on running a water injection system since I'd like the extra margin of safety with the 11.5:1 compression pistons.


***Had to brake it into 2 posts
 

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Discussion Starter #2 (Edited)
VE is a tough one for me to guess on my engine, I've got some decent stock cams, and with the dual cam profiles and variable timing on the intake camshaft I'm guessing my VE should be fairly good. Also my intake manifold is a good free flowing design and I have it port matched to the head. The engine bone stock was dino'ed at 160 whp and is rated at 180 crank hp from the factory. And adding an aftermarket exhaust and cold air intake put another 12 whp to that to increase it to 172 whp naturally aspirated. My understanding is this all points to a good VE number. I'm sure I'm above the 90% ve but I don't know how much. I plotted all the maps with 90% ve (with yellow dots) and 100% ve (with red dots) because I figure I will be somewhere between these 2 numbers.

There are 3 kits out, but only 1 that I can actually buy since the other 2 kits are backordered and have people that have waited over 1 year and still don't have their kits.

** all the compressor maps below have numbers corrected to an altitude of 3,750 ft because that is the altitude I live at (near the rocky mountains).

XS Engineering (kit is back ordered)
Turbo = IHI VF23 turbo, I can't find a compressor map for this turbo


SF Kit (kit is back ordered)
Turbo = Garrett T3 Super 30 trim




C2 Kit (avalible)
Turbo = Garret GT28R or GT28RS


GT28RS

Turbine
-Wheel: 53.85mm w/ 76 trim
-Housing: .64 or .86 ar

Compressor
-Wheel: 60mm w/ 62 trim
-Housing: .60 ar





GT28R

Turbine
-Wheel: 53mm w/ 62 trim
-Housing: .64 ar

Compressor
-Wheel: 60mm w/ 60 trim
-Housing: .60 ar





Also the GT2871r is available and could be swapped in instead of the gt28r or gt28rs, but I have yet to find a map. I also think the GT2871r may be too big of a turbo for my application and I would be subject to big turbo lag problems. I found this thread on here particularly interesting on the GT2871r;

http://www.mr2oc.com/showthread.php?t=73020&highlight=gt2871

GT2871r

Turbine
-Wheel: 53.85mm w/ 76 trim
-Housing: .86 ar

Compressor
-Wheel: 71mm w/ 56 or 48 trim
-Housing: .60 ar


I used 3000 rpm as my low end because everyone with the gt28r and gt28rs says they are at 8 psi of boost by 3000 rpm.

Here is the chart I used to get the numbers, I corrected the numbers for an altitude of 3,750 ft;




This is what I understand about the choke line;
Choke line: The maximum centrifugal compressor volume flow rate is normally limited by the cross-section at the compressor inlet. When the flow at the wheel inlet reaches sonic velocity, no further flow rate increase is possible. The choke line can be recognised by the steeply descending speed lines at the right on the compressor map.
So now I'm stuck wondering what I should do at this point, I'm running low boost (6 & 8 psi) so I don't need a big turbo, but my CFM's seem to be too high. How should I go about this? is there a trick that I don't know about? I also know HKS has a line of turbo's but I can't find compressor maps for them.

Any useful information or suggestions would be greatly appreciated, I'm sorry this is not more 3sgte related but I'm stuck and don't know where else to go at this point.

Thanks,
War
 

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I would be simply amazed if you saw 100% VE. I know those 2zzges are amazing engines, but I think 100% is even out of their range.

The US 3S-GTE has a compression ratio of 8.8, not 9.1. Sorry, I had to split that hair.

Lastly, you are putting too much emphasis on the compressor map, and not enough on the turbine. The turbine that will achieve 8 psi at 3000 RPM will choke long before 9500 RPM, and the turbine that doesn't have flow issues at 9500 RPM won't have the energy to boost to 8 psi at 3000 RPM.

Turbine maps, annoyingly enough, are hard to come by.
 

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Discussion Starter #4
flyboy said:
I would be simply amazed if you saw 100% VE. I know those 2zzges are amazing engines, but I think 100% is even out of their range.

The US 3S-GTE has a compression ratio of 8.8, not 9.1. Sorry, I had to split that hair.

Lastly, you are putting too much emphasis on the compressor map, and not enough on the turbine. The turbine that will achieve 8 psi at 3000 RPM will choke long before 9500 RPM, and the turbine that doesn't have flow issues at 9500 RPM won't have the energy to boost to 8 psi at 3000 RPM.

Turbine maps, annoyingly enough, are hard to come by.

I've now been told 9.1, 8.8, and 8.5 compression ratio for the 3sgte, sorry I don't know which one is correct.

I have turbine maps for the GT28r and GT28rs, I can't find good information on how to read or plot on them though, do you have a link that would give me better turbine map information?
 

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I agree... your VE estimates at 9000rpm are a little high I think...

have you got a dyno plot of your engine as it is? the torque curve can give a good indication of how your VE is over the RPM range..

have you also taken into account that the turbine side of any of those turbos is going to choke the motor a bit at high RPM, therefore reducing VE as the revs go up?

-Tristan
 

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Figure out what the corrected mass flowrate coming out of the engine in terms of combustion gasses. Use the plot to see where it starts to choke (flow doesn't increase with increasing pressure). As for boost threshold, that's much trickier. You can use thermo to figure out energy in and out type of stuff, but that still won't give you things like boost threshold shifts with valve overlap. Basically, for boost threshold, you just have to experiment unless you can really accurately model your engine, which I can't do.

One more note. If you expect a lot of exhaust manifold backpressure (small turbine), then valve overlap isn't your friend. I understand the high-RPM side of the 2zz's cams have quite a bit of overlap.
 

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I have been discussing this with WAR for weeks. From the maps we have been looking at he would need a turbo that would be good to 350 -400hp for us 3SGTE guys inorder to get his engine into the 250 range and still be on the island.

Now 9000rpm is a pretty high redline but it isn't monsterously higher than ours. There have also been a number of guys that have taken the 3SGTE to those RPMs so this isn't breaking new ground. We have seen guys up their VE with cams and intakes and valve work on our engines and have their curves still climbing like crazy at redline even with relativly mild turbos. If I remember correctly Jeffs graph was an example of one still heading up hill at redline.

So what I don't get is why he would need so much turbo in order to stay on the island.

The numbers for VE that I have seen tossed around for the 3SGTE are ~90 in stock trim and 95 for big exhaust, cams and intake. Having seen the 2ZZ in action, helped take it apart and looked at it's specs I have to beleive that it has to have atleast as good of VE as a 3SGTE with those mods. Does any one know what the VE of a stock Caldena engine is?

BTW WAR has a couple thousand hours wrenching on my 91T and will be co-driving it in solo2 this summer so I hope you guys can help him out.
 

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Maybe a custom turbo is the go... garrett make a hell of a lot of compressors. Im not a compressor map expert... but doesnt a larger trim compressor tend to stretch its legs in terms of flow at any given boost level? perhaps a less conventional compressor fitted to a GT28RS style turbo would be worth considering...

-Tristan
 

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He, like everybody, needs to decide if he wants low-end torque or high-end power. Low-end torque means early spool (low boost threshold), while high-end power means breathability and lag.
 

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You can't have both really. You can't have a responsive low end if you want a killer high end. You are trying to put a tiny turbine on a motor that will choke it at 3/4 the way through the rpm range.

Since you have the high rpm modifications on the car already, I think you should look at a larger turbine to accomodate 9500 rpms.

We have a 7200 rpm redline and we try to get turbos that spool at around 3500 or less which gives us nice power in the top 1/2 of our power band. If you take your 9500 rpm redline and u divide it in half you get 4200 rpm. So I'd look into a turbo that spools to give you power in the 4200 - 9500 rpm.

Just my 2 cents.
 

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If you use a smaller, responsive turbo, then your VE will drop off very quickly in the high-end, preventing the compressor from choking. See how the torque drops off in the high-end on the 2nd chart? That's as a result of the VE dropping very low. That will keep you off of the choke line.
 

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Moving all that air under low pressure is going to take a big turbo.

Your pressure ratios seem a little low to me. I would allow for 0.5# loss across the air filter & piping and for 1# loss across the IC & piping.

As stated above, valve overlap is not your friend with a turbo motor. Exhaust backpressure will exceed boost pressure and reduce volumetric efficiency at higher rpms.

These other guys who see 8# at 3000 rpm. Which turbine are they running? 0.64 A/R? Or 0.86 A/R? General design rule-of-thumb is to assume full boost at 1/2 of redline rpm. I don't think you can get full boost by 3000 without choking at 9500. Actually, that might not be the best choice of words. Efficiency will be dropping, but you won't necessarily be at the choke line. The actual choke line is somewhere near the end of the highest rpm line.
 

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WAR said:
I have turbine maps for the GT28r and GT28rs, I can't find good information on how to read or plot on them though, do you have a link that would give me better turbine map information?
Check out the "Performance Dictionary - Turbine Efficiency" article in the July 2002 SCC magazine. J. Kavanagh (Garrett Eng.) describes its importance and what impacts it. He compares two GT turbos that have the same turbines but different compressors and analyzes their turbine maps. You may recognize the specs to be those of the GT28RS and HKS GT2540 (Ext.B. GT25R). I hope that helps.

I have a hard time imagining how you're going to plot flow requirements for a 6500 rpm powerband on a single compressor map. You asked what happens when you fall off the map and into the choke area. Everyone with a stock turbo at higher boost certainly does that, and in my case I didn't notice anything other than the continuing gradual reduction in torque. I imagine comp. outlet temps go through the roof as well! When I installed the GT28RS I could tell that power wasn't dropping off nearly as quickly even though somewhere above 6500 I was falling off of its map as well according to my calculations. I suspect that comp. outlet temps are far lower with the GT and that final dyno tuning will allow for more advance and power without detonation for this reason.

Bruce
 

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Discussion Starter #16
twoina2 said:
Moving all that air under low pressure is going to take a big turbo.

Your pressure ratios seem a little low to me. I would allow for 0.5# loss across the air filter & piping and for 1# loss across the IC & piping.

As stated above, valve overlap is not your friend with a turbo motor. Exhaust backpressure will exceed boost pressure and reduce volumetric efficiency at higher rpms.

These other guys who see 8# at 3000 rpm. Which turbine are they running? 0.64 A/R? Or 0.86 A/R? General design rule-of-thumb is to assume full boost at 1/2 of redline rpm. I don't think you can get full boost by 3000 without choking at 9500. Actually, that might not be the best choice of words. Efficiency will be dropping, but you won't necessarily be at the choke line. The actual choke line is somewhere near the end of the highest rpm line.
Your right I pulled a complete idiot job on the psi drop, I forgot to add that in. Here is a new sheet with the turbo run to 7.5 and 9.5 to compensate for a 1.5 drop across the system.




If my VE will drop off to at high rpms then that would be great and keep me on the compressor map. If I drop to 80%VE by 9500 rpm then I will land on the compressor map in a decent point.




Thanks for the help everyone, I didn't realize the VE would drop off so much from the turbine end, I was also worried that if I went past the choke line that I would cause serisous damage to the turbo or engine. If my ve is going to drop off and the turbo is going to become less efficent and all I'm going to loose is some HP then I'm fine with that. I just didn't want some weird turbo stuff happen that would distroy it or the engine.

I know that overlap at the high rpm range isn't going to be my friend, the lowest overlap I can have at high rpm is 55 degrees. I hope that I can adjust the overlap at the low and mid rpm's to find a optimal spool/hp setting. What does the 3sgte run for stock over lap?

I'm told by people with the GT28RS and GT28R that they are seeing 8 psi of boost before 3000 rpm. The GT28RS is reported to be fully spooled in the 2800 to 2900 rpm range and the GT28R is reported to be a bit faster, but I haven't herd an exact rpm number on the GT28R.
 

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Ask for pressure vs. RPM data from the turbo makers in your neck of the woods. People will lie all the time about boost threshold. If someone wants to sell you a turbo, they should tell you which gear the pull was done in on the dyno, what the boost vs. RPM is and (preferably) what the AFR and ignition timing was. All of these things affect when the turbo sees full boost.
 

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I think the 3sgte has zero overlap with their cam profile...unless you go to something realy big like 288.


T
 

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Yes, the stock 3SGTE overlap is zero at 0.020. I've watched some of the guys with aftermaket cams and overlap is still low, maybe 10-15 degrees at 0.020.
 
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