SMALL single turbo project, thoughts welcome! - Page 9

ZephTheChef · #**121** 12-01-2010, 04:31 PM

I had to double-check before I started shopping, so don't feel bad. It is backwards compared to some manufacturers (AC Delco maybe?).

Nevin · #**122** 12-01-2010, 04:33 PM

I think delco and autolite are the other way around fromm NGK. You're right there. I learned of this when I wanted some colder plugs for my mazda a while back and found out that a colder one just plain old didn't cross to anything!

And that's a handy chart!

ZephTheChef · #**123** 12-01-2010, 04:37 PM

Quote:

Originally Posted by Nevin

I think delco and autolite are the other way around fromm NGK. You're right there. I learned of this when I wanted some colder plugs for my mazda a while back and found out that a colder one just plain old didn't cross to anything!

And that's a handy chart!

Just noticed you've got a Ford Probe. My first car was a 1995 Ford Probe GT. Loaded up. I miss that car, it was a whole lot of fun. I'll probably get another one someday...knowing what I know now about cars, I could really have some fun with it

ZephTheChef · #**124** 12-01-2010, 07:20 PM

I've been doing some fun turbo-spool math based upon a spool data chart that we put together over on the 3000GT/Stealth forums. If the numbers from twins on a 3.0 can be directly related to a single on a 3.3, then I've come up with some shockingly quick spool predictions. The 16Gs on a 3/S will start seeing positive pressure around 1800rpm at full load. Divide that by 2.2 (10% more displacement, and twice the cylinders feeding the turbo) and you get 818 RPM. Max boost happens at 4700RPM on a 3/S, the same formula yields 2136 RPM with a single on the SVX. There are obvious flaws and things not considered here (compression ratio, differences in VE, differences in EGT, etc), but it should give a general idea of the spool characteristics anyway.

If that's even remotely representative of what I'll be seeing, then I should get positive boost off-idle, which will hit around 30psi by 2136 RPM, and make about 215 crank HP at that point. That'll ramp up to about 365HP at 4000RPM, at which point the turbo will be out of flow and the boost will start bleeding off, maintaining somewhere around that 365HP to redline (the boost falling off, but maintaining roughly the same CFM).

When plotting that on the compressor flow map it just BARELY stays right of the surge line, this is of course helped with higher VEs, as I'm sure I'll be seeing due to the boost. I think this turbo is going to be an incredibly fun match if the real-life numbers look anything like these guesstimates. 200+HP from 2000 RPM...hellz yeah! It's so borderline to being too small that it'll either fall on it's face, or spool fast and hard, I can't wait to see which.

NeedForSpeed · #**125** 12-01-2010, 07:26 PM

Great work, super thread

ZephTheChef · #**126** 12-01-2010, 07:53 PM

If I do end up with surge at lower RPMs, I have a plan that involves recirculating a small amount air from the pressure side to the suction side of the turbo to increase the airflow through the compressor a little bit and keep the wheel from stalling out. Perhaps use some sort of valve that shuts at 15psi or so (which is where I should be out of the danger zone of being close to the surge line) so that I can then put everything that's coming out of the turbo into the engine.

Any ideas? Not that I'm going to plan on doing anything right off the bat, but I like to have a backup plan to deal with things that I know might potentially be problems.

SVXRide · #**127** 12-01-2010, 09:28 PM

Something about 30psi and 10:1 compression is making me wonder how long the piston ring lands will stay together...

-Bill

LetItSnow · #**128** 12-01-2010, 09:36 PM

Quote:

Originally Posted by SVXRide

Something about 30psi and 10:1 compression is making me wonder how long the piston ring lands will stay together...

-Bill

I don't even want to think about the temperature calculations on that!

Cam · #**129** 12-01-2010, 10:30 PM

I doubt the engine will be reliable at all. But a cool project, none the less. LAN is selling his shortblock. It would be perfect for this.

ZephTheChef · #**130** 12-02-2010, 01:51 PM

I doubt it'll spike to 30 in real-world situations, but mid to high 20s is a strong possibility. And keep in mind, we're talking that much boost at lower RPM ranges, I predict it will bleed off to 8-10psi by redline, and we're talking about a peak HP of 360-380 crank. It's NOT very much power, relatively speaking, and I see no reason the engine shouldn't be capable of much more than that reliably if it's tuned properly.

I have no idea what kind of AFRs the other forced-induction guys have run, but from the general attitude I've seen around here about tuning, it sounds like many people have run what, to me, is scary lean...and that seems to have everyone on the boards scared to death of boost.

Most turbo cars from the factory run as rich as 10:1 during boost on gasoline, and you don't see much leaner than about 12.2:1 in boost. Sometimes a bit leaner just off-boost to promote hotter EGTs and thereby better spool, more like 13:1. 10:1 is obviously way too rich to make the best power, but on gasoline that's often what's required to avoid detonation.

E85 is another animal. You won't hit detonation from running lean, but it doesn't make good power there either, and the EGTs get up there pretty good when you get lean. You can actually get into more trouble running rich because you're more likely to run into pre-ignition. I'm going to keep it right in the middle to start and run 12.1:1. I should have enough flow out of my injectors to hit the 365HP at about 60psi of base fuel pressure, which gives me plenty of wiggle-room with the second fuel pump.

I'm not saying I expect the engine to last another 100,000 miles, but I don't see any reason it shouldn't last another 50,000. I'm much more concerned about the rest of the drivetrain...particularly the already fussy automatic transmission that I'll have in there until I get around to the 5-speed swap.

ZephTheChef · #**131** 12-02-2010, 02:02 PM

Quote:

Originally Posted by LetItSnow

I don't even want to think about the temperature calculations on that!

Let me scare you a little bit more. I have a nitrous kit laying around, and I may need to spray a little bit of nitrous to keep my intake temps down enough to stay inside the compressor flow map for this turbo. I'm thinking that would be a simpler, more effective solution than venting some of the boost back into the compressor inlet. A 30 shot should be plenty, lower my intake temps some 50-75 degrees and add a little boost of power as well.

httrdd · #**132** 12-02-2010, 02:31 PM

Wow nitrous does that?

ZephTheChef · #**133** 12-02-2010, 02:39 PM

Quote:

Originally Posted by httrdd

Wow nitrous does that?

Is that supposed to be sarcasm directed at me always explaining why I'm doing what I'm doing, or are you genuinely asking?

In the case of the latter, yes. Liquid nitrous oxide is some 100 degrees below zero, so if you squirt it in your intake, it cools the charge tremendously. A small shot from my wet kit will be safe, have a fairly long life between bottle refills, and help keep my VE higher so that I stay right of the surge limits of the compressor flow map.

oab_au · #**134** 12-02-2010, 03:05 PM

Quote:

Originally Posted by ZephTheChef663884

,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,E85 is another animal. You won't hit detonation from running lean, but it doesn't make good power there either, and the EGTs get up there pretty good when you get lean. You can actually get into more trouble running rich because you're more likely to run into pre-ignition. I'm going to keep it right in the middle to start and run 12.1:1. I should have enough flow out of my injectors to hit the 365HP at about 60psi of base fuel pressure, which gives me plenty of wiggle-room with the second fuel pump.,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

12.1:1 A/F? It will be interesting to see how this goes, as 9:1 is the usual E85 A/F ratio, with rich at about 7:1.

Harvey.

httrdd · #**135** 12-02-2010, 03:11 PM

Quote:

Originally Posted by ZephTheChef

Is that supposed to be sarcasm directed at me always explaining why I'm doing what I'm doing, or are you genuinely asking?

In the case of the latter, yes. Liquid nitrous oxide is some 100 degrees below zero, so if you squirt it in your intake, it cools the charge tremendously. A small shot from my wet kit will be safe, have a fairly long life between bottle refills, and help keep my VE higher so that I stay right of the surge limits of the compressor flow map.

Ok got ya.