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VVT Head & Manifolds onto a NA8 block
Posted: Wed Mar 18, 2009 10:36 pm
by Woo
Helping out a friend, so any info would be good.
He has an NA8 with cams etc, but wants a bit more oommph
So he's got hold of a VVT head, manifolds and ECU
My question is what are the possible drawbacks (if any) and benifits of mating an early block with a late head?
clearances? piston shape? comp ratio? etc
any thoughts?
Bazz
VVT Head & Manifolds onto a NA8 block
Posted: Thu Mar 19, 2009 12:34 pm
by manga_blue
The head bolts on but all the sensors are different. There are no issues with the block or pistons, etc. You have 2 choices, both are big jobs needing a lot of wiring skill.
1. Re-wire half the NA8 car to take the NB sensors, NB ECU and all its engine and ECU wiring looms. Could be a major hassle as there are NB things like immobiliser, ecu dríven fuel pump and alternator control, etc which just don't exist on the NA.
2. Use as much as possible of the NA8 bits/sensors, the NA8 loom and either the NA8 ECU or an aftermarket one (Hydra does VVT, megasquirt does not yet). Main ones are:
- NA8 crank angle sensor (bolts straight on)
- Choice of NA or NB MAF and IAT (and you'd also have to do something about fuel adjustments. Jaycar DFA would be good enough.)
- NA8 throttle body and sensors
- NA8 fuel rail and return
- NB coil on plug system (cut existing NA8 wires to coilpacks and splice on NB wiring loom leads to COPs instead)
- NA8 alternator
- etc, etc
VVT can be enabled well enough with non-VVT ECUs by adding RPM switches to send voltage to the VVT oil control solenoid. Easiest method is to run 0-1700rpm at full inlet cam retard (0V), 1700-5200rp at full advance (+12V), 5200+ at full retard (0V).
Otherwise VVT can be ignored by leaving the solenid off which gives full retard. This still gives reasonable power but just a bit weaker through the mid-range.
Heaps of info on miata.net and miataturbo.net but it takes a lot of finding
Have fun!
VVT Head & Manifolds onto a NA8 block
Posted: Thu Mar 19, 2009 1:38 pm
by bruce
In a nutshell - stick it in the bin!
VVT Head & Manifolds onto a NA8 block
Posted: Thu Mar 19, 2009 2:58 pm
by manga_blue
VVT Head & Manifolds onto a NA8 block
Posted: Thu Mar 19, 2009 5:20 pm
by Mr Morlock
My head is spinning Manga Blue- very impressive knowledge. The feedback on the forum particularly on the electronics side is extra good.
VVT Head & Manifolds onto a NA8 block
Posted: Fri Mar 20, 2009 9:40 am
by Woo
manga_blue wrote:... except that there are 12-15kw and a wide power band just waiting there if you want to put in the effort.
Exactly what we were thinking too
We are indebted to you Magna_blue, much appreciated
It's going in a rally car that we're not allowed to put an aftermarket ECU in or turbo on. This is gonna be fun
Keep you posted
Cheers
VVT Head & Manifolds onto a NA8 block
Posted: Fri Mar 20, 2009 5:11 pm
by manga_blue
Thanks. Obviously I went deeply into it as an option just recently but decided it was just too much work, opting instead just to clean up an NA8 head a bit.
The VVT would have been nice though. The part where NB8Bs always get the drop on me is the extra low end grunt they have getting out of the slower corners. While NB8As and NB8Bs both have roughly the same max Kw it's the spread that counts.