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#1 davemac

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Posted 17 April 2017 - 03:47 PM

over the last year ive been slowly! building a new motor for my na, im using a mk2 bottom end and mk2 head.

I'm concerned now that i should find a good mk2.5 bottom end as its stronger or so im told.

http://i1081.photobu...tv.jpg~original

Thoughts?


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#2 davemac

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Posted 17 April 2017 - 03:54 PM

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#3 davemac

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Posted 17 April 2017 - 03:56 PM

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#4 Markcoopers

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Posted 17 April 2017 - 04:59 PM

I think it all comes down to what you want the motor to do, and dare I say it you are worried about nothing. If you are aiming at the limits of the engine then a stronger starting point is good, but if you are well within those limits you are worrying about nothing.

You said ITB build, so can not really see this at the limits of the bottom end, many FI engines are over 250/280bhp and large tourque numbers and they are not granading.
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#5 davemac

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Posted 17 April 2017 - 05:44 PM

I'm hoping for around 170 bhp so not big power being na.
I've been through bottom end and its all good, engines low milage so maybe I should carry on.
Using danst manifold on respaced gsxr 40mm itb's,
with ported and skimmed head.
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#6 Markcoopers

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Posted 17 April 2017 - 07:40 PM

At that level I think you will be absolutely fine, carry on.

However when you say ported and skimmed, how much did you take off? I ask as when you take off big amounts the compression really does ramp up and while the Dyno will give you a loverly number, piston rings can take a bit of a pounding under the stresses.

Also, and I am not an expert here, but 170 is quite a big number from essentially just head work. I am under the impression that the mk2 head is not a bad flow to start with, so it is about compression and the swirl from the 3 angle valve seats......and this is tricky and way beyond my abilities or advice. Surfice that just ITB's and a good ecu map, don't get despondent if only 160 comes up....it will still be a good motor

Good luck and hats off for you trying.
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#7 davemac

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Posted 17 April 2017 - 10:31 PM

I'm changing the cams as well I think they are 254 with 10.15 lift.
Took 40 thou off the head.
As garage Quinn motors did but I think his wbhp numbers are optimistic.
Well see when its on dyno.
Ive got to finish my 90 v8 Landrover restoration first.
So I'll have to wait
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#8 davemac

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Posted 17 April 2017 - 10:39 PM

20111126_162516_zpsrso1ybxt.jpg
My old s4 with ko4's mrc map made good power that was a lot easier all bolt on :)
Wanted to go na again in mx5
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#9 davemac

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Posted 19 April 2017 - 07:45 PM

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#10 Markcoopers

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Posted 19 April 2017 - 08:32 PM

Are those ITB's with blanked off injector bosses, so as to use the original direct to head injectors and fuel rail? Is that how they come from danst engineering or have y cleaned and spaced them?
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#11 davemac

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Posted 19 April 2017 - 08:49 PM

I sent him some itb's.
He's spaced them and yes I'm using original fuel rail etc keeping it simple as possible
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#12 davemac

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Posted 19 April 2017 - 08:59 PM

Its his manifold, trumpets and modified back plate.
All very well engineered I very happy with service and product.
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#13 Markcoopers

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Posted 20 April 2017 - 06:28 AM

Hum....I too am looking at ITBs but was rather discounting the bike ones as the vibrations and air leaks around seals can be an issue in car applications. But I guess it all comes down to your own prep and installation?

I was looking at butterfly bodies with no bosses on a jenvey manifold set up, but those do look very good
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#14 davemac

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Posted 20 April 2017 - 06:36 AM

The itb's I'm using still maintain the original rubber "tubes" so hopefully good seal.
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#15 davemac

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Posted 20 April 2017 - 06:48 AM

They were off a 1999 gsxr SRAD 750 bike had done 16k so hopefully not to worn.
He gave me the option of using the bike injectors of mx5 ones.
I went with the mx5 ones so I can use his ecu which uses all the original sensors wiring etc. Pnp as much as possible
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#16 Markcoopers

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Posted 20 April 2017 - 06:09 PM

Ono is my plan, but with MS not the ME221 thing.....just the advice I was given and trust. Keen to see how you get on as pretty much what I am looking at all be it on a mk1 1.8
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#17 mbh69

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Posted 20 April 2017 - 07:39 PM

I've got the blink stage 2 power upgrade and the Jenveys are awesome but I do think without headwork and cams all you'll notice is an awesome noise.
I got 138bhp at the wheels, I'm hoping to do a high compression bottom end next and possibly raise the Rev limiter a little too.
Awesome on track though.
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#18 davemac

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Posted 20 April 2017 - 08:57 PM

Yeah hopefully the higher compression/headwork and cams will help.
Garage Quinn on youtube is getting good power.
It'll be a while till I get motor in car though.
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#19 Dickie

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Posted 08 July 2017 - 07:38 PM

Hi Folks,

I have just purchased Davemacs ITB set up.

He has decided to go a different route.

It will be going into a Mk1 Eunos with MK2 skimmed gas flowed head with piper 285 cams onto a MK2.5 bottom end.

 

I have just modified the GSXR throttle wheel to take  a standard Mx5 throttle wheel. 

I removed the cable holder from the bike bodies leaving the throttle stop part.

I drilled out the rivets holding the mazda unit together then fitted the Mazda unit onto the GSXR with two 3mm machine screws countersunk to leave the inside face flush where the return spring resides.

This will allow exactly the same pedal ratio as per the Mazda throttle body.

I am hoping that when I fit it all to the engine that original throttle cable will be long enough ( If not I have a brand new Supercharger length cable which will be a little over length )

If I fit an airbox instead of the pipercross filter I will need to re route the cable anyway.

 

Cheers Dickie


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#20 davemac

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Posted 10 July 2017 - 06:19 AM

That's great dickie.
So you might go with a plenum chamber and air box.
Be alot quieter I'd of thought.
Good luck
Cheers
Dave
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