MR2 SpyderChat banner
1 - 20 of 21 Posts

·
Registered
Joined
·
3,208 Posts
Discussion Starter · #1 ·
O.K., here's one that I don't understand entirely (among many, of course) what effect does a smaller/larger A/R have on output, all other things being equal?

I know that the smaller A/R will spool up more quickly, but does it also limit output on the high end of the scale?

For instance, if a GT25 is available with either a .48 or .63 A/R and the same 60 trim, what would be the general effect of the smaller one on the output curves?
 

·
Super Moderator
Joined
·
3,303 Posts


A smaller A/R will maintain a higher gas velocity thus helping the turbo to spool faster, but this smaller housing also has a limited volume that it can flow compared to a housing with a larger A/R, so this could be a limiting factor for peak output. There are tons of other variables, but basically, smaller A/R higher velocity lower volume, larger A/R lower velocity higher volume. At least that's how I understand it with my very limited knowledge of turbo chargers.
 

·
Registered
Joined
·
3,208 Posts
Discussion Starter · #3 ·


A smaller A/R will maintain a higher gas velocity thus helping the turbo to spool faster, but this smaller housing also has a limited volume that it can flow compared to a housing with a larger A/R, so this could be a limiting factor for peak output. There are tons of other variables, but basically, smaller A/R higher velocity lower volume, larger A/R lower velocity higher volume.
So the overall effect of a .48 vs a .63 would be that it would spool faster, but that maximum flow volume would be reduced all other things being equal, right? So as long as the maximum flow volume/power output I want is achievable with the smaller A/R I'm going to have more power sooner, and not limit the total power, right?

My goal is more torque sooner, and not to worry too much about ultimate numbers, but I don't want to cut myself short either.
 

·
Registered
Joined
·
2,575 Posts
So the overall effect of a .48 vs a .63 would be that it would spool faster, but that maximum flow volume would be reduced all other things being equal, right? So as long as the maximum flow volume/power output I want is achievable with the smaller A/R I'm going to have more power sooner, and not limit the total power, right?

My goal is more torque sooner, and not to worry too much about ultimate numbers, but I don't want to cut myself short either.
Also keep in mind there's both a compressor and turbine A/R
 

·
Registered
Joined
·
8,484 Posts
The efficiency map of the turbo is more important than the AR. You also have to consider whether if the turbo has a dual ball bearings.

There are so many different variations of each turbo that I just look at the efficiency map.
 

·
Registered
Joined
·
2,575 Posts

·
Registered
Joined
·
3,033 Posts
You also have to look at engine size, low revving, high revving, etc. If you really have questions regarding choosing a good A/R consulting the turbo manufacturer & give them your vehicle specifications and your goals for your vehicle (autox, road racing, drag racing, daily, etc.). The turbo manufacturer will guide you in choosing the best setup for your vehicle.
 

·
Registered
Joined
·
3,208 Posts
Discussion Starter · #10 ·
You also have to look at engine size, low revving, high revving, etc. If you really have questions regarding choosing a good A/R consulting the turbo manufacturer & give them your vehicle specifications and your goals for your vehicle (autox, road racing, drag racing, daily, etc.). The turbo manufacturer will guide you in choosing the best setup for your vehicle.
Thanks, I know, but if you talk to three guys building or selling turbos you'll get three answers, which is pretty normal in commerce.

I want to UNDERSTAND THE PROCESS and make an informed decision.

I've presented my goals to a couple of resellers and my tuner shop, and I've been told, among other things:

1. Ball bearing turbos are a must.
2. For small, relatively low power applications journal bearing turbos are O.K.
3. Get a T3/T4 and it'll do the job.
4. A T3/T4 won't work, get a GT28 because you can make the big power (I don't want to).
5. Get an OEM turbo from Mitsubishi, Saab or another like sized factory application.
6. Don't use an OEM turbo from another application.
7. Get a .50 trim.
8. Get a .60 trim.

All of the people have been helpful, enthusiastic, and sure they were on target.

At some point I want to make the call, and I want to know why I'm making it. My first venture into warming up my car went wrong, and I ultimately made the decisions so I'm responsible for it.

For Spyder 2.0 I want to get it right the first time. Or first two times.

:D
 

·
Registered
Joined
·
8,484 Posts
I would stick with shops that have actually built a turbo for a 1zz. They cost more but you pay for the experience and won't have to to redo your build.

Don't aim for a hp number. Set a boost level you want to run and pick the best turbo for that boost. Whatever hp you get is what you get. With a 1zz 8psi is about perfect for both power and reliability.

Piecing together your own kit vs buying an already made kit is not really much cheaper. I think either of the off the shelf kits for the spyder are price low enough that it's not really worth designing a whole new kit.

Why not just buy a turbokits.com kit, install it move on?
 

·
Registered
Joined
·
3,208 Posts
Discussion Starter · #12 ·
I would stick with shops that have actually built a turbo for a 1zz. They cost more but you pay for the experience and won't have to to redo your build.

Don't aim for a hp number. Set a boost level you want to run and pick the best turbo for that boost. Whatever hp you get is what you get. With a 1zz 8psi is about perfect for both power and reliability.

Piecing together your own kit vs buying an already made kit is not really much cheaper. I think either of the off the shelf kits for the spyder are price low enough that it's not really worth designing a whole new kit.

Why not just buy a turbokits.com kit, install it move on?
The MWR and Turbokits ready made setups both use a bigger turbo (GT28) working not too hard and seem to favor a drag racing/top speed mindset. Mat at MWR said he could tame one down a little, but in my mind that says that a smaller turbo might work better for my goals. The TurboKits setup uses alcohol injection, I don't want that.

The over riding consideration is that I want to be involved in the process and understand it.

The money is a secondary consideration, but if a $650 turbo will give me what I want, why spend $1,300 ? ? ?

I liked the thinking of the PE setup; smaller turbo, early spool up, full boost a little sooner, but with 225-235 hp and torque as close to 200 as possible.

The process interests me.
 

·
Registered
Joined
·
8,484 Posts
The PE setup was not a great kit. It didn't use any intercooling at all. The problem is magnified with a small turbo that generates more heat at the same boost level. 200-225 hp means 8-10 psi with the PE turbo without an intercooler, really putting the engine at risk with knock. Realistic safe hp was closer to 170-185hp.

Why use a small non ball bearing turbo if a slighly larger ball bearing turbo can spool the same and be more efficient.

If money is not a problem then you can have a water intercooler installed in the intake piping of the Turbokits turbo kit, no need to purchase the water/methanol injection, Or you can keep the water injection as added intercooling, upgrade to a GT turbo and run a PFC.
 

·
Registered
Joined
·
3,208 Posts
Discussion Starter · #14 ·
The PE setup was not a great kit. It didn't use any intercooling at all. The problem is magnified with a small turbo that generates more heat at the same boost level. 200-225 hp means 8-10 psi with the PE turbo without an intercooler, really putting the engine at risk with knock. Realistic safe hp was closer to 170-185hp.

Why use a small non ball bearing turbo if a slighly larger ball bearing turbo can spool the same and be more efficient.

If money is not a problem then you can have a water intercooler installed in the intake piping of the Turbokits turbo kit, no need to purchase the water/methanol injection, Or you can keep the water injection as added intercooling, upgrade to a GT turbo and run a PFC.
I want it to be as simple as possible, which is why the PE was attractive, and I don't want 250+ hp which both the current "ready-made" kits talk about starting with and going up from there, but don't mind an A/A intercooler being in the loop, which takes away some of shortcomings of the PE.

In answer to your comment; "Why use a small non ball bearing turbo if a slighly larger ball bearing turbo can spool the same and be more efficient." I've got a question, what would constitute "more efficient"? What's the benefit? And why wouldn't something like a GT25 be much more appropriate for my goals than a GT28?

The engine has been rebuilt with Wiseco pistons and the MWR forged rods so I'm thinking the boost could probably be more in the 10-12 range, but I also want to see if I can get it done and stay OBDII compliant in Washington.

It's something for me to hobby shop on that's fun. I probably am going to a lot more trouble than I need to, but I'm having fun with it, and appreciate everybody's input.
 

·
Registered
Joined
·
8,484 Posts
Turbos generate heat. The more boost you run with a small turbo the more heat you generate the less power at that boost you make.

To be OBDII compliant means having to use a piggy back.
 

·
Registered
Joined
·
3,208 Posts
Discussion Starter · #16 ·
Turbos generate heat. The more boost you run with a small turbo the more heat you generate the less power at that boost you make.

To be OBDII compliant means having to use a piggy back.
I know. That's why I think that a GT25 with either a .48 or .63 A/R with a yet to be determined trim, a large(ish) A/A intercooler and an AEM F/IC (fuel and ignition) piggyback will work. I still don't understand the .45 .50 .60 trim business, but I'm learning.

I was a mechanical engineering major 40 years ago, I just wasn't very good at it.

:D

We'll see, and I do always appreciate your time and thoughts. I'm a bit of a head banger, and I know it, sometimes a little slow on the uptake.

I listened to everybody and got the stuff I did on the first go around; ported and polished head, PPE header and downpipe/cat, Crower cams and a fuel controller hoping to get around 20 hp and 15 lb/ft of toque, I got 13 hp but above 6,000 rpms, and the torque figure actually dropped. Spent maybe $4K, then a valve broke and blew the whole gig.

So, now I've got forged internals, a lot of numbers flying around in my head, and a determination to have a better idea what the result is before I write the checks this time around.

Big fun actually.

:D
 

·
Registered
Joined
·
8,484 Posts
I listened to everybody and got the stuff I did on the first go around; ported and polished head, PPE header and downpipe/cat, Crower cams and a fuel controller hoping to get around 20 hp and 15 lb/ft of toque, I got 13 hp but above 6,000 rpms, and the torque figure actually dropped. Spent maybe $4K, then a valve broke and blew the whole gig.


:D
This is why it's a waste of time and money to build an NA 1zz or even a 2zz. The high dollar/hp for an NA build is just not worth it.:(

I'll warn you again. The turbo won't ever run 100% right with a piggy back. You will have to run something like an E-manage and just won't have full control or things like VVT. Been there, done that.
 

·
Registered
Joined
·
3,208 Posts
Discussion Starter · #18 ·
This is why it's a waste of time and money to build an NA 1zz or even a 2zz. The high dollar/hp for an NA build is just not worth it.:(

I'll warn you again. The turbo won't ever run 100% right with a piggy back. You will have to run something like an E-manage and just won't have full control or things like VVT. Been there, done that.
Actually I think that if I would have skipped the PPE header and went with the gutted stocker, used their down-pipe and cat, kept the Crower stage 1 cams and not used the opened up head I might have been happy with the result. If there would have been 12-15 lb/ft of torque and 15-20 hp I might have been done. I think I "outsmarted" myself, or "out-stupid-ed" myself, as it were.

I'm not sure what kind of VVT changes I might want to make if I'm sticking with the stock valve train and don't want to go beyond the 6,500 rpm redline, and I admit that I don't know what effect the turbo will have on that aspect of it, and would like to understand that better, but my thought is that with control over fuel and ignition I can get a pretty good thing going. If all else fails a PF/C is only a little more, and I can sell off the Apexi Neo, the AEM F/IC, the PPE header and downpipe, and all the rest of the crap piling up in the garage for beer money, or, if it looks like it won't work, just sell this thing and get myself an Exige 240 and take a yoga class so I can get in and out of it.

:D
 

·
Registered
Joined
·
9,840 Posts
Most shops specialize in what they know. Asking them what turbo YOU and YOUR car (not their specialty) should get will get varied answers like you've experienced.

A little story: When I was piecing together my turbo kit for my nissan I did all the math (garret or honeywell use to have a great turbo tutorial with math guidance on their site). From the math and efficiency charts about 3 turbo families met my needs. 1 was kinda small, 1 was just right and 1 was slightly bigger than my needs. Of course being the hot blooded male I must get the one that is two sizes too big :lol: A while later I actually got to speak to a Garret rep at a vendor show I worked at and of course he quickly recommended the smaller sized of the turbo that was just right. I left his booth thinking this guy didn't know anything at all about turbos :lol:

Moral of the story is get what you need. I think you already know what you want you car and power to feel like after and I think you'll definitely be happy with the GT25 snail (until you start getting the itch). It will definitely boost fast and power will be in the lower rpm range and teeter out on top, just like a stock turbo'd car might do, but better.

Did a quick search for you.
Here we go, read learn decide for yourself.
http://www.turbobygarrett.com/turbobygarrett/turbo_tech_advanced
 

·
Registered
Joined
·
3,208 Posts
Discussion Starter · #20 ·
Most shops specialize in what they know. Asking them what turbo YOU and YOUR car (not their specialty) should get will get varied answers like you've experienced.

A little story: When I was piecing together my turbo kit for my nissan I did all the math (garret or honeywell use to have a great turbo tutorial with math guidance on their site). From the math and efficiency charts about 3 turbo families met my needs. 1 was kinda small, 1 was just right and 1 was slightly bigger than my needs. Of course being the hot blooded male I must get the one that is two sizes too big :lol: A while later I actually got to speak to a Garret rep at a vendor show I worked at and of course he quickly recommended the smaller sized of the turbo that was just right. I left his booth thinking this guy didn't know anything at all about turbos :lol:

Moral of the story is get what you need. I think you already know what you want you car and power to feel like after and I think you'll definitely be happy with the GT25 snail (until you start getting the itch). It will definitely boost fast and power will be in the lower rpm range and teeter out on top, just like a stock turbo'd car might do, but better.

Did a quick search for you.
Here we go, read learn decide for yourself.
http://www.turbobygarrett.com/turbobygarrett/turbo_tech_advanced
Thanks man, I'd seen their site but missed that info.
 
1 - 20 of 21 Posts
Top