jon
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Post by jon on Jun 7, 2019 8:37:25 GMT
I'll be running the mk2 inlet manifold and not the flat top mk2.5. Have you got all the VICS gubbins and an RPM switch to control it if you are on the standard ECU?
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Post by scottydugg on Jun 7, 2019 8:44:33 GMT
I'll be running the mk2 inlet manifold and not the flat top mk2.5. Have you got all the VICS gubbins and an RPM switch to control it if you are on the standard ECU? I'll have the manifold with the bits, but I won't have a way of driving it. I haven't found any info on what is required to get it working but had seen you can jam it permanently open. So any help on that would be greatly appreciated, thanks.
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jon
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Post by jon on Jun 7, 2019 8:54:20 GMT
It's run by the solenoid on the back - this uses vacuum to open/close the butterflies.
The standard switch point is ~5200RPM. From memory the solenoid is switched to earth below 5200RPM, unswitched above 5200RPM. It should be fairly easy with an RPM switch circuit.
If you jam it open / closed you are either going to compromise top end or bottom end and probably lose a considerable amount of power...
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Post by scottydugg on Jun 7, 2019 9:03:37 GMT
It's run by the solenoid on the back - this uses vacuum to open/close the butterflies. The standard switch point is ~5200RPM. From memory the solenoid is switched to earth below 5200RPM, unswitched above 5200RPM. It should be fairly easy with an RPM switch circuit. If you jam it open / closed you are either going to compromise top end or bottom end and probably lose a considerable amount of power... Regarding the jamming open, I was hoping that wasn't the case but that was daft. Ok will check I'm getting that with my parts and try dig up some more information on how people have done it before me. Edit: www.mx5nutz.com/forum/index.php?showtopic=191793 The first search brought up this. Also here: forum.miata.net/vb/showthread.php?t=326518Post #12 details and has a link to a FLyin Miata dyno sheet comparing running/not running VICS
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jon
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Post by jon on Jun 7, 2019 9:29:14 GMT
Are you ever planning on doing more than just the engine swap?
I'd seriously consider skipping the RPM activated switch (which appear to be over £100 on their own) and just straight to a standalone ECU - which will control the VICS and get you a whole load more functionality as well - and if well mapped a bit more power than the standard ECU as well..
Or if you are on a budget and don't mind a bit of work, swap to the mk2 ECU which will run the VICS - not sure of the VICS NBs had a knock sensor or if it was just the later ones but that's another bonus..
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jon
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Post by jon on Jun 7, 2019 9:29:51 GMT
Or swap to a square top manifold
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Post by scottydugg on Jun 7, 2019 9:41:43 GMT
Or swap to a square top manifold Does it remove VICS? For the cost of the switch which seems to be $45, I could maybe source a flat top manifold, as long as all the other mk2 hardware fits. I'll be running the stock bottom end and running off the stock ECU for now (who knows for the future). BTW updated my post above with information regarding VICS that I've found.
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jon
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Post by jon on Jun 7, 2019 9:54:39 GMT
Yep - the square top doesn't have VICS or any other complexities.
Square tops are definitely the preferred option for FI usage, working VICS is supposed to yield a little more midrange at the expense of top end, however I've not seen a scientific back to back comparison of how much is really in it...
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Post by scottydugg on Jun 7, 2019 10:16:42 GMT
Yep - the square top doesn't have VICS or any other complexities. Square tops are definitely the preferred option for FI usage, working VICS is supposed to yield a little more midrange at the expense of top end, however I've not seen a scientific back to back comparison of how much is really in it... Ah excellent, so future proofing against any FI plans I might not have yet This is the only info I can see on VICS being engages against not: "Here's our '99 with 600 miles on stock engine, FM single n/a exhaust. If you look at the chart, Run 29 is with hose disconnected and plugged for the VICS actuator. Major drop in midrange torque. Run 30 is with VICS hooked up normally. Run 31 is with VICS locked in the low rpm position, you can see that peak hp is the same, but hp plummets after about 6k rpm." Dyno Graph Here: www.flyinmiata.com/tech/dyno_runs/99_050400.pdf No Comparison against a flat top and operational VICS though. I can't see anything regarding stock cam gear and a skim however. 40thou seems to be the maximum you can go whilst maintaining non-interference but I can't see anything about variable cam gears becoming an absolute must. Need to figure out the max skim for the standard cam gears.
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Post by wannabe on Jun 7, 2019 10:36:03 GMT
I can't see anything regarding stock cam gear and a skim however. 40thou seems to be the maximum you can go whilst maintaining non-interference but I can't see anything about variable cam gears becoming an absolute must. Need to figure out the max skim for the standard cam gears. This observation is not helping my confidence for my seemingly skimmed-to-the-max head lol
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Post by FFS Corders on Jun 7, 2019 10:46:08 GMT
If not using an RPM switch, best option is run a switched live directly to the solenoid so it is held in low RPM. As per the FM thread above, it means it drives well up to peak power then drops off - which is what a mk1 does anyway. If you compare a mk1 Dyno vs a BP4W Dyno the VICS is shown by the MK2 holding bhp for longer up to the limiter. I'm sure I put my Dyno results in the Dyno thread showing my mk1 engine then after I fitted a complete MK2 BP4W with rpm switch
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Post by scottydugg on Jun 7, 2019 13:09:12 GMT
I can't see anything regarding stock cam gear and a skim however. 40thou seems to be the maximum you can go whilst maintaining non-interference but I can't see anything about variable cam gears becoming an absolute must. Need to figure out the max skim for the standard cam gears. This observation is not helping my confidence for my seemingly skimmed-to-the-max head lol I think it can vary from head to head, how much of a skim have you gone for? I believe too much of a skim leads to retardation of the timing and the variable gears are needed to bring it back into where it should be. BUT, I'm clueless about this stuff at present so only repeating what I've read on the internet. If not using an RPM switch, best option is run a switched live directly to the solenoid so it is held in low RPM. As per the FM thread above, it means it drives well up to peak power then drops off - which is what a mk1 does anyway. If you compare a mk1 Dyno vs a BP4W Dyno the VICS is shown by the MK2 holding bhp for longer up to the limiter. I'm sure I put my Dyno results in the Dyno thread showing my mk1 engine then after I fitted a complete MK2 BP4W with rpm switch Your guide was very helpful, I think I'm just seeing if I can source a mk2.5 inlet manifold vs. ordering the switch. I doubt I'd notice the difference so it's more a man maths situation.
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Post by FFS Corders on Jun 7, 2019 13:27:54 GMT
It's certainly a more straightforward option. Sourcing an RPM switch is pretty long winded unless you can make one
Be interesting to see the Dyno graph with a flat top on BP4W head.
Bear in mind that you will want to retain the MK1 throttle body as the sensor connections on MK2 are different. Plus the body will be further back so needs the shorter MK2 throttle cable, unless you are good at shortening them of course!
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jon
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Post by jon on Jun 7, 2019 14:03:56 GMT
Bear in mind that you will want to retain the MK1 throttle body as the sensor connections on MK2 are different. Plus the body will be further back so needs the shorter MK2 throttle cable, unless you are good at shortening them of course! If you make a small plate about an inch long you can move the mk1 throttle cable up to take up the slack - this is how mine is currently fitted until I get round to swapping over to a mk2 cable. If you are going to the hassle of swapping I'd probably fit the mk2 throttle body too and swap the connections over as the IAC plumbing is much neater. Again, another job on my list!
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Post by scottydugg on Jun 7, 2019 14:21:46 GMT
It's certainly a more straightforward option. Sourcing an RPM switch is pretty long winded unless you can make one Be interesting to see the Dyno graph with a flat top on BP4W head. Bear in mind that you will want to retain the MK1 throttle body as the sensor connections on MK2 are different. Plus the body will be further back so needs the shorter MK2 throttle cable, unless you are good at shortening them of course! Bear in mind that you will want to retain the MK1 throttle body as the sensor connections on MK2 are different. Plus the body will be further back so needs the shorter MK2 throttle cable, unless you are good at shortening them of course! If you make a small plate about an inch long you can move the mk1 throttle cable up to take up the slack - this is how mine is currently fitted until I get round to swapping over to a mk2 cable. If you are going to the hassle of swapping I'd probably fit the mk2 throttle body too and swap the connections over as the IAC plumbing is much neater. Again, another job on my list! Simple swap is now bordering a much larger project If I can source parts I'll try and do it the correct way, perhaps if it starts spiralling I'll do it in stages. Already thinking if the heads getting swapped now is as good a time as any to fit a coolant re-route kit. I'll keep this up to date with a parts list when I get a chance.
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