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i am thinking about building my 95 for ITBs... how would i go about with this? like what compression pistons and all of that. most likely i will be using a 6 speed transmission and a 3.9 torsen. i am probably going to dish out the cash for a maxim works header and some sort of single exhaust, unless i can get my hands on a center exit shotgun. the stroker kit from flyin miata has also crossed my mind with this build...

i know i can throw itbs on my car as is, but i want more power. i dont want that turbo or supercharger junk, i want itb with full capability of being 100% reliable and daily driveable.

so does anyone have any pointers?
 

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here is one way to go all motor. :)
for street i wouldn't go over 11:1 compression. and i'm partial to the holley efi system for a stand alone ecu.
 

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Hi there ive built a 1600 na running jenvey itb bodies and dta s40 pro ecu (very reliable setup) that was an almost std setup with a ported/ skimmed head and a std bottom end, with a day of mapping on the rolling road it produced 148bhp this was 10.5:1 compression ratio and was not enough really.


My new build is an 1800 mk2 na engine, i will be posting a thread this week on the build if you care to take a look but here is the spec and a pic of the finnished article:
1800 NA from mk2 mx5, squish band on the pistons were machined down by 0.045" as well as the block and the cylinder head, this took the compression ratio up to 11.5:1 on the std pistons and rods (the pistons also need to be pocketed for the valves if this is done), the head was ported quite a bit and finnished off to a high standard but still on std size valves, this engine is also running a DTA S40pro ecu and custom wiring loom and with all the work carried out as above and with only std cams it produced 178bhp and again a very strong engine to drive. its not hard to get good power from an engine with std bits
 

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thats hot
 

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With regards to the c/r it depends what you are wanting to atchive realy, if you want big power you need to up your c/r with a set of pistons or do what i did in mine and have a machine shop do the work, i also built a street 1800 mk1 engine of similar spec to mine for a friend and his was running CP pistons at 12;1 compression ratio he drove this car every day to work and back and he said that not only did it drive easy but like mine it got better on fuel with the DTA ecu (and the right mapper).

So it can be done for road engines aswell, all you need to do is sacrifice a bit of top end power by using the standard cams and up the C/R to fill out the mid range torque.

my full start to finnish engine build will be on here soon so look out for it.
 

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really? tried it?
I'm 10.8 on 87 octane :shrug:
nope most of my builds have 8:1. general rule of thumb for 93 octane is 11:1. you can run more but it will have the best street manors at 11:1
 

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Kieran, is that an extra set of ITB's in the ground there? If so whatcha gonna do with those? And need to read build thread with engine sounds
 

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I have considered IRTB's for my stock bottom end (9:1 CR), but I almost intend to have a street performance headwork done with +1mm intake valves and either a Maxim Works or a Racing Beat header. Something like this should make around 160whp with very nice low end and midrange torque. This should allow for the use of 87 octane fuel.
 

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brontosaurus
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No way in hell are you making 160whp at 9:1. Ditch the idea of 87 if you are dumping lots of money into an NA build. You need high compression to make power naturally aspirated. There was recently a build with TWM throttles, toda cams, solid lifters, 11:1 85mm pistons so roughly ~1900cc, etc all very high end stuff and he could barelly break into the 170s.

160whp+ is going to require ~11:1cr or higher, major head work preferably on a 99 head, cams, ITBs or worked over intake manifold, etc

You need compression and you need octane to fight the off detonation it can cause. You'll be spending a whole lot of money on nothing if you don't accept that.
 

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Just a thought...... water/meth injection with IRTBs to run more compression/prevent detonation..... I'd love to see someone figure out how to set that up. :woolery:
 

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brontosaurus
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Meth injection has been done on ITBs. You just need a really good fail safe setup if you are using meth injection as a secondary fuel. Without it you can really ruin an engine fast if there is any problem with delivery.

Building an N/A engine rarely makes sense if ultimate power is your end goal. Some people just like them, and you can't say a ~180whp N/A miata wouldn't be a lot of fun. Different strokes for different folks. Arguing otherwise is a waste.






P.S. I'd be worry about methanol eating at the resin on these velocity stacks.

 

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Just curious do you guys run an idle air valve with your IRTB setups?

Currently my Jenvey setup is being tuned and I am having issues with getting a stable idle espy with the A/C switched on.


I built my high comp B6 motor for ITB eventuality because where I am, engine swaps and F/I are highly illegal.
 

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Kieran, is that an extra set of ITB's in the ground there? If so whatcha gonna do with those? And need to read build thread with engine sounds
Those are for an all steel vauxhall corsa motor i was building for a nova stage rally car.
i can supply jenvey products now at -10% of the jenvey prices if anyone is interested...
 

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1800 NA from mk2 mx5, squish band on the pistons were machined down by 0.045" as well as the block and the cylinder head, this took the compression ratio up to 11.5:1 on the std pistons and rods (the pistons also need to be pocketed for the valves if this is done), the head was ported quite a bit and finnished off to a high standard but still on std size valves, this engine is also running a DTA S40pro ecu and custom wiring loom and with all the work carried out as above and with only std cams it produced 178bhp and again a very strong engine to drive. its not hard to get good power from an engine with std bits
was this on a chassis dyno?
 

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My new build is an 1800 mk2 na engine, i will be posting a thread this week on the build if you care to take a look but here is the spec and a pic of the finnished article:
1800 NA from mk2 mx5, squish band on the pistons were machined down by 0.045" as well as the block and the cylinder head, this took the compression ratio up to 11.5:1 on the std pistons and rods (the pistons also need to be pocketed for the valves if this is done), the head was ported quite a bit and finnished off to a high standard but still on std size valves, this engine is also running a DTA S40pro ecu and custom wiring loom and with all the work carried out as above and with only std cams it produced 178bhp and again a very strong engine to drive. its not hard to get good power from an engine with std bits

I call BS. Read my build. My engine is a ton more radical than this and is not yet making that much power. Unless you just fudged all the correction numbers on your dyno and it was -50 degrees out side. My car was dynoed on dynojet uncorrected and it was almost 100 degrees
 

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i dont know how much it NEEDS them? I tried to find a pre made kit or something but the only place that has it is flyin miata and I refuse to pay their rediculous prices for anything. Im not good with electronics so i dont want to try and make them myself
 

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brontosaurus
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Trackspeed engineering sells Cops kits for $300.

Try and hit up flying miata, see what they'd sell the ls3 coil setup without the coils. I bet they are selling brand new ones with the kit. You can source used ones for much much cheaper.
 
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