Endurance racing LSJ Miata Swap - Cobalt SS Network



2.0L LSJ Performance Tech 205hp Supercharged SS tuner version. 200 lb-ft of torque
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Old 05-16-2018, 07:41 PM   #1  
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Endurance racing LSJ Miata Swap

Hi everyone,

I need some recommendations. We are building an 02 Miata to endurance road race. I originally bought an LNF with transmission from an 08 solstice to swap into the car. We have since decided the tuning is going to be a nightmare. I now plan to buy an LSJ to use instead.

We will modify the supercharger snout to fit and add a cable throttle body. ECU will be a Megasquirt MS3 pro. All the cooling mods and a huge heat exchanger for the intercooler will be used. Fuel is restricted to 93 octane. Rev limiter will be set at 7k. Full 3 inch straight exhaust with header.

I want to get 240-250whp that can be beat on for 8 hours a few times a year. Can these motors handle that? What other mods should I do? I'd like to keep the longblock as stock as possible.

Am I asking too much?

Thanks
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Old 05-16-2018, 09:08 PM   #2  
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Personally if I was going to push it hard for 8 hrs at a time I would put good rods and pistons in it, crank should be ok. The last thing you want is engine failure. Now if it was only going to be an hour or something that's different.
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Old 05-16-2018, 09:23 PM   #3  
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Maybe someone could chime in if the stock oil cooler can handle that. Seems to work well but maybe a external front mount would be nice.

I'd think if you kept the oil temp under control you'd be golden
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Old 05-16-2018, 09:25 PM   #4  
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I planned to do a remote front mount oil cooler. Forgot to mention it. Transmission and rearend will also have coolers, plus one for the driver 😉
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Old 05-17-2018, 11:11 AM   #5  
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Nova, if I have to do rods and pistons I would go the Le5/9 route and put an LSJ blower on it. How stout are the internals of the LSJ
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Old 05-17-2018, 03:13 PM   #6  
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Ecotec 3.0 for life!
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Old 05-17-2018, 05:46 PM   #7  
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Quote:
Originally Posted by LSJMiata
Nova, if I have to do rods and pistons I would go the Le5/9 route and put an LSJ blower on it. How stout are the internals of the LSJ
Internals are good, but to ask stock stuff to run close to flat out on many cars for 8 hrs at a time is asking a lot. It's not like you are hot lapping for 15 minutes and letting it set for 30.
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Old 05-18-2018, 10:58 AM   #8  
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lol le5 internals
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Old 05-18-2018, 11:27 AM   #9  
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lol le5 internals
I meant putting a forged rotating assembly in an LE5 if I'm upgrading internals
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Old 05-18-2018, 11:37 AM   #10  
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I meant putting a forged rotating assembly in an LE5 if I'm upgrading internals
the le5 has a dog **** rod to stroke ratio 1.54 your best bet would be to run a lsj crank in a le5 block with a 2.2 rod raise the compression to 11.5 so you can keep the blower in its most efficient range and re sleeve the block with better sleeves then stock so you will be able to setup the piston to wall clearances and it will also give you better ring control and run a lsj head
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Old 05-18-2018, 11:57 AM   #11  
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Originally Posted by mrbelvedere View Post
the le5 has a dog **** rod to stroke ratio 1.54 your best bet would be to run a lsj crank in a le5 block with a 2.2 rod raise the compression to 11.5 so you can keep the blower in its most efficient range and re sleeve the block with better sleeves then stock so you will be able to setup the piston to wall clearances and it will also give you better ring control and run a lsj head
Gotcha, I like the idea. I still have the LNF. Can it be resleeved to take 2.4 pistons?
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Old 05-18-2018, 01:13 PM   #12  
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No, you need a 2.4 block for 88mm pistons unless you wanna pay for big boy sleeves.
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Old 05-18-2018, 02:00 PM   #13  
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Quote:
Originally Posted by mrbelvedere View Post
the le5 has a dog **** rod to stroke ratio 1.54 your best bet would be to run a lsj crank in a le5 block with a 2.2 rod raise the compression to 11.5 so you can keep the blower in its most efficient range and re sleeve the block with better sleeves then stock so you will be able to setup the piston to wall clearances and it will also give you better ring control and run a lsj head
Not a lot of advantages to the lower R-S ratio but there are some:
Shorter rods mean the overall height of the block can be shorter, which means the overall weight of the block can be lighter. The engine will typically pull more vacuum at low RPM, which means better throttle response and low end torque (good for street performance and everyday driving). Spark timing can be advanced a few degrees for some additional low speed torque, and the engine is less prone to detonation, which can be a plus in turbocharged, supercharged or nitrous applications.
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Old 05-18-2018, 02:23 PM   #14  
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Ecotec blocks are all the same height.
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Old 05-18-2018, 02:32 PM   #15  
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Originally Posted by Slowbalt2000 View Post
Ecotec blocks are all the same height.
"Shorter rods mean the overall height of the block can be shorter"

Being the same was a manufacturing decision to cut costs.
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Old 05-18-2018, 03:06 PM   #16  
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Not a lot of advantages to the lower R-S ratio but there are some:
Shorter rods mean the overall height of the block can be shorter, which means the overall weight of the block can be lighter. The engine will typically pull more vacuum at low RPM, which means better throttle response and low end torque (good for street performance and everyday driving). Spark timing can be advanced a few degrees for some additional low speed torque, and the engine is less prone to detonation, which can be a plus in turbocharged, supercharged or nitrous applications.
you are right on rod to stroke ratio the higher the rod to stroke ratio is easier on the rotating assembly the piston side load on the thrust sides of the pistons a lot less then on a lower rod to stroke ratio the piston so you get a friction loss less wear on the rings and pistons and cylinders and rod bearings from less rod angle the acceleration from tdc is slower so it does not yank the piston down it also fills the cylinder better and will force a **** head to flow more air for better cylinder filling the old school way of lower compression for force inducted engines is just that old you raise the compression slow the blower down and keeping it where its most efficient will make you more money then low compression high boost

low rod to stroke ratio heavy rod angle accelerated wear on the thrust sides on the piston and rings and rod bearings higher piston speeds cylinder head does not flow as well and less cylinder filling its harder on the pistons and pins when going through tdc you raise compression and increase boost you just make things harder on the rotating assembly now you talk about running a short rod and shortening up the deck for weight loss on a overhead cammed engine when you bring the cams closer to the crank you retard cam timing so now you have to add a bunch of timing to make up for the slow cam timing and that can be hard on rod bearings as well

Last edited by mrbelvedere; 05-19-2018 at 02:50 PM.
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Old 05-18-2018, 03:07 PM   #17  
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Quote:
Originally Posted by HGT View Post
"Shorter rods mean the overall height of the block can be shorter"

Being the same was a manufacturing decision to cut costs.
when a company does that they have to change the cam timing
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Old 05-18-2018, 03:50 PM   #18  
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Quote:
Originally Posted by HGT View Post
"Shorter rods mean the overall height of the block can be shorter"

Being the same was a manufacturing decision to cut costs.
Well thats not really a benefit then, now is it?
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Old 05-18-2018, 05:25 PM   #19  
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Not if we are being specific to the Ecotec block....
Like I said... Not a lot of advantages.
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Old 05-18-2018, 05:41 PM   #20  
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Edited above

Last edited by HGT; 05-19-2018 at 05:16 PM.
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Old 05-18-2018, 05:44 PM   #21  
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when a company does that they have to change the cam timing
I am sure those that are doing that as a weight saving measure are accounting for that as well.
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Old 05-19-2018, 09:37 AM   #22  
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In any engine I have ever seen built for rpm and efficiency the higher the rod ratio the better. Longer rods also allow you to use shorter pistons (wrist pin height) which saves weight, and makes the engine easier to rev and take rpm.
The 406 I have in the Nova came with a crappy ratio I went from 5.56 rods to 5.7 and if I wanted to do more clearance work I could have went 6.0. Cut down on piston weight, and allowed me to be able to spin the motor a little higher.
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Old 05-19-2018, 01:35 PM   #23  
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Originally Posted by HGT View Post
I am sure those that are doing that as a weight saving measure are accounting for that as well.
you cant account for the cam timing like your thinking a company like zzp probably could not account for it gm could

Last edited by mrbelvedere; 05-19-2018 at 02:55 PM.
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