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Old 01-25-2010, 06:44 AM   #1
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Default Stroker engine questions.

To start, I'm currently in Afghanistan. I only have you guys as a Miata lifeline. What has been on my mind lately is my upcoming engine build. Yes I searched but all the discussions end up side tracked.

First my goals. (Click on my link for more info) I want to build the engine to take full advantage of the 3071 and 750cc injectors. I am thinking boost limited to 18psi to keep the engine living for a while. The transmission will end up 6 speed.

Now, the question is whether to stroke the engine to 2.0. My hope is to be above the 350hp range, it may require a 2.0 to reach this with my above goals. Based on parts that I already have; would the stroker be worth the extra cash? I am not so sure. Do I want one? Hell yes.
Flyin` Miata stroker kit $4999
Maruha 2.1 L Stroker Kit $5300
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Old 01-25-2010, 08:12 AM   #2
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To make that kind of safe power, you should be thinking about some good internal parts whether you stroke the engine or not. Stroking the motor will be more expensive, and you will have much more into it than the cost of the kit. You can never beat more cubic inches, however the biggest question you have to ask yourself is if it is in your budget.

Add up all the costs that will be associated with the build, and then come up with a budget you can afford. Eliminate the upgrades you can not afford but you can live without, and wallah, you have yourself an engine.
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Old 01-25-2010, 08:52 AM   #3
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Given your goal 350rwhp and the high cost of 2.0/2.1L stroker kits, wouldn't an FE3 swap be more cost effective? The stroker kits are not going to give you the benefit of the FE3's better cylinder head and will require more boost to make the same power.
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Old 01-25-2010, 11:44 PM   #4
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I considered a V8 swap before buying the turbo but being in the Army I dont have the time for the car to sit on jacks for weeks. So without getting side tracked.

When build time comes the engine will be filled with high quality parts, just not sure about the stroker. That one dicision changes the build price about $2500.

I guess what I am kicking around is the idea of balanced parts. If the compressor is only good for X amout of flow and the injectors are only good for X amount of fuel will the stroker get me in the sweet spot or over < X. I have a map of my compressor that is plotted for a 2.0 at 2 bar. It looks to be far over to the right and high.

Damn I feel lazy asking this but the only internet I have is my work computer that I share with 6 coworkers. I am going to search for injector sizing and try to figure out what my compressor will support.
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Old 01-25-2010, 11:50 PM   #5
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You can do big power without the stroker, but the extra displacement makes it easier.
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Old 01-26-2010, 12:28 AM   #6
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Quote:
Originally Posted by Savington View Post
You can do big power without the stroker, but the extra displacement makes it easier.


I'd probably do the FM motor for convenience.

if you want a street rat then fine, but if you ever plan to track this car I strongly suggest more modest power levels.
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Old 01-27-2010, 01:39 AM   #7
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I'd probably do the FM motor for convenience.

if you want a street rat then fine, but if you ever plan to track this car I strongly suggest more modest power levels.
Well, I have been to several HPDE's and will continue to go when I get back. I am glad you brought that to my attention. With the stroker I could turn the boost down on the track and rely on the displacement to spool the turbo earlier.

Also, like Sav said. It would be easier to reach my power levels with a larger engine.

So, after digging around some other sites I see that my 750 injectors will support up to 400 with the right pressure. So I donít need to worry about those. I also looked at the Garrett site to see what my turbo would support but I donít know what trim it came with. I e-mailed FM to ask them what trim my turbo was sent with.

More later.
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Old 01-27-2010, 01:52 AM   #8
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I think the 350 is doable but your not gonna have alot of room to play at 18 psi on a 1.8 overall if done effectivly it will be more hp than you can reasonable use on the street anyway.
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Old 01-27-2010, 02:45 AM   #9
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No, you don't need a stroker. GT3071+built nonstroked motor is a combination that has been successfully executed on the miata many times. Stroker will spool faster, make moar power everywhere, but seriously, unless you're rich, don't waste your money. If I had to spend that extra $2500 on my car I would spend it on... a brand new factory hardtop!
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Old 01-27-2010, 04:09 AM   #10
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There are a lot of places I'd spend $3200 in a Miata before I dumped it into a stroker kit. A good LSD and high-dollar suspension are a good start.
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Old 01-27-2010, 08:24 AM   #11
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There are a lot of places I'd spend $3200 in a Miata before I dumped it into a stroker kit. A good LSD and high-dollar suspension are a good start.
AFCO's already done. I have the torsen now but the 4.30's are killing me. 1st is gone in a heart beat. A MS rear with 3.90's and a 6 speed is on my list of to do's. FM anti-sway bars will be here soon. Brakes and wheels? Done.

The engine is what is on my list when I get back from hell. I see some here have 1.9 on their signature info. How are you getting 1.9? Bore?
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Old 01-27-2010, 02:13 PM   #12
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Quote:
Originally Posted by faeflora View Post
Stroker will spool faster, make moar power everywhere
How noticeable is this difference?

I’ve been thinking for a long time if a stroker kit is really worth it when having a big turbo like the 3071. The difference in displacement sounds quite small. The FM Stroker kit increases displacement about 8.4% and the overbore pistons increase displacement too but not that much.
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Old 01-27-2010, 04:41 PM   #13
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Do it if only because there are not enough 2 litre miatas in the world. And just think of the bragging rights The rest of the car seems pretty much sorted or about to be sorted so it deserves an engine to match.

Good Luck with the build
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Old 01-27-2010, 04:59 PM   #14
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Quote:
Originally Posted by Duckie_uk View Post
Do it if only because there are not enough 2 litre miatas in the world. And just think of the bragging rights The rest of the car seems pretty much sorted or about to be sorted so it deserves an engine to match.

Good Luck with the build
Yeah, regular old forged pistons and rods aren't good enough.

Dyno sheets comparing regular built motors to strokers can be found on flyin miatas site.
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Old 01-27-2010, 06:23 PM   #15
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If you want to read the parts list of somebody who is putting down 350whp+, here's one:
https://www.miataturbo.net/forum/t11340/ That is CEO. He's for real. And he has a 2.0 stroker.
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Old 01-27-2010, 06:24 PM   #16
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Quote:
Originally Posted by faeflora View Post
Yeah, regular old forged pistons and rods aren't good enough.
Quote:
would the stroker be worth the extra cash? I am not so sure. Do I want one? Hell yes.
This sounds like a man who wants to justify what he is about to do. I was merely trying to encourage the guy. Yes you can do everything he is asking for with a "stock" built engine but hey! Why not go large? To be entirely honest its nice to see a thread that's not a budget build discussion or a "what can I get away with not doing enquiry".
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Old 01-27-2010, 11:37 PM   #17
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I know MRM is working on a less expensive 2.0 stroker solution. The rumor is someone local will be running one soon.

McCully Racing Motors- There's no Replacement for Displacement.
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Old 01-28-2010, 12:01 AM   #18
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Quote:
Originally Posted by DOHCPanther View Post
AFCO's already done. I have the torsen now but the 4.30's are killing me. 1st is gone in a heart beat. A MS rear with 3.90's and a 6 speed is on my list of to do's. FM anti-sway bars will be here soon. Brakes and wheels? Done.

The engine is what is on my list when I get back from hell. I see some here have 1.9 on their signature info. How are you getting 1.9? Bore?
Fm sways aren't stiff enough IMO I didn't like mine at all, went with a big Rb hollow.

Yup 1929cc with an overbore here too.
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Old 01-28-2010, 12:15 AM   #19
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Well, I got a reply from Jeremy but he didn't send the turbine information. So I still dont know exactly what my turbo will support. When I go to the Garrett site the info they provide is 300 to 460. There are three A/R avalable for the turbine.

Well, im getting kicked off see ya.
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Old 01-28-2010, 12:43 AM   #20
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The GT3071R that FM specs is a 0.63 A/R, IIRC.

I'm running FM's stroker motor with 750 cc/min injectors and this turbo. It's a sweet combination, with low-end grunt with an addictive mid-range. Top end maxes out at about 7,500 rpm, but unless I change the cams and perhaps the intake manifold, I'll have to live with it

Regarding fueling: Even at 400+ rwhp, I still had lots of injector capacity left.

If you're going to spring for a stroker, my advice is to go with the FM kit. It's been tested to ludicrous power levels (550-800 rwhp) and, more importantly, the rod ratio (when coupled with their rods/pistons) is kept stock for "revability". The MRM kit appears to get the displacement only through increased bore, so you won't get the low-end torque a stroker affords.

Have fun - I know I do.
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