'97 Mk1 MX-5 V6 - Weights and Measures

[gryphon]

I'm not despairing yet, don't worry!

Jan 13, 2020 19:12:25 GMT goldnrust said:

These things are sent to try us! Still sounds like you're making progress.

It still sounds to me like your problem is related to air imbalance between the left and right banks. You've checked all the injectors are working and are releasing similar amounts of fuel, and you've checked that all the spark plugs are firing (hopefully in the right order/at the right time!) and as you say by doing a compression test you can be fairly sure one of the cams isn't miles out.

So both banks are getting the same fuel and same spark, it only leaves an air imbalance ot give such a big difference in AFR reading (presuming both sensors work correctly, you could always swap them left to right and see if the problem changes banks?)

11:1 AFR is about right for a cold start, so I'd be looking or air leaks on the side that's lean. When you said you synchronised the throttles, did you do that with a vacuum gauge, or one of those air flow meters? Because the air flow type wont account for any vacuum leaks.

p.s. hang in there! It'll all come good and you'll be swearing at yourself for having not seen the problem earlier.

Rather solid summary there I am somewhat hopeful that I fixed one air leak from the ICV, and cleaned and reassembled everything from the intake ports upwards. The one start I did sounded like an improvement but didn't have time for any more testing... and the horizontal rain put me off this evening.

I synchronised the throttlebodies with a flow meter in the intake - as you say, it can't measure a vac leak. What I also did was borrow a set of vacuum gauges from a friend over the weekend - need to make some adapters to plumb them in, but if I still have different exhaust manifold temps I'll see what they can tell me.

AFR wise, I could have a duff sensor, but they tell the same story as the exhaust manifold temperatures. Also I forgot to say but the spark plugs are clearing up - right bank ones are starting to look a little lean, left bank no longer wet, but I'm not sure the engine has run enough to get a good read from them. I also don't have a blowtorch to clean them properly, but it will get done soon.

The P.S. rings too true...

Jan 13, 2020 21:11:00 GMT cb11acd said:

I can't help, or contribute anything useful apart from words of encouragement

*Because I want a go in it*

Thanks! You know this is all your fault - I remember you enthusiastically sending me an evo article about a V6 MX-5 swap that hadn't altered the weight balance a few years back... You play the long game very well.

[gryphon]

Two more tests done now it's stopped raining!

Started the engine and put a hand on each exhaust manifold. Within 10 seconds right bank is too hot to touch, left one is just starting to feel warm. My hope was misplaced!

Which leads to vacuum gauges. Made some quick adapters and plugged them in in place of the PCV valve and brake booster. I tested running without those first and saw no change in behaviour, so testing without them should give relevant results.

Of the two connected gauges the left is the right bank, right is the left bank... So left gauge is the lean side. Only issue is they look pretty even to me - lean bank is showing slightly higher vacuum so I think that rules out a vac leak being the cause.

Running the engine cold the misfire was more severe than last time. Big "chunk" sound from the engine every few seconds but still not regular.

So, two problems. Right bank running very lean and left bank (I think) misfiring.

Vacuum pretty equal between banks

Compression 170 on cyl4 (left bank), 190 on the rest

Injectors spray pattern visually good, fuel volumes equal

Visual check of sparks was ok.

Other than the misfire it actually runs rather well

_______________________________

After writing the above my neighbour (a mechanic who's just opened his own garage) was free to listen to the engine for a few minutes... started it up and the misfire had almost disappeared, and it ran rather nicely! Proper sods law. The exhausts were the same however - he agreed that one side was far too hot (radiating heat like mad), the other side too cold - you could almost touch it after a few minutes running and revving... But the idle was spot on and engine sounded pretty sweet other than the misfire.

His suggestion was check for restrictions in the exhaust on the hot side before it joins the single pipe but was surprised how well it was running considering. Going to try running on just the exhaust headers and see if there's any change. Sorry neighbours!

Yet to check - ignition timing... different coils - again...

Beginning to definitely need the ECU diagnostics.

Edit - been talking to people and doing some more googleing. I'm not sure why I didn't immediately spend time googling - it's normally my first reaction to anything I don't know! What it does point to in this case is my cam timing is a little out. My suspicion is exhaust cam is a little advanced on the hot side which wouldn't show in the compression test and would be putting still combusting gasses into the exhaust. Guess that's my Saturday plans made.

[gryphon]

Way back in this thread when I was putting the engine back together I wrote this:

Aug 19, 2019 14:05:45 GMT gryphon said:

All my timing marks lined up and the engine spins freely but I still bolted the front cover on with a gnawing worry in my gut that it might not be right! Somehow I never get that with belts - I've always been confident that I've got it right. First time with a chain engine, and a V engine, and my gut was tying knots!

Turns out I should have listened more to my gut.

I disconnected the exhaust from the manifolds, started the engine and put my hand over each exit. Hot side was putting about twice as much air out as the cold side - despite showing the same vacuum! Something definitely wrong here.

Some googling later and talking it through with some guys at work the penny dropped. I had followed my timing marks exactly when I put the engine back together everything was timed well, it made good compression - but there are two banks, and when I reassembled it I hadn't thought about making sure that they were in sync with each other. The cams turn 360* for every 720* of the crank, so if I lined the timing marks on one bank 360* out on the crank vs the other bank I'd have one bank doing exhaust stroke when it should be compression, intake stroke when it should be power etc.

Sooo... back to taking everything apart again!

Would be nice to say I'm getting quicker at it but including dodging rain showers (used that time to sort out the radio wiring... It was trying to feed 12v into a speaker output!) it still took me the best part of two days start to finish.

I also fitted an IL motorsport radiator with a slimline fan and mounts for an oil cooler while I was at it.

Oil cooler not fitted for now but I think I'll be needing it. Will take a little modifying to fit it in though, as currently the water pump intake sits where the cooler will want to...

But enough procrastination -

She runs

I'm hoping that the smoke will clear up and isn't there because my mistake has caused some damage...

[procrastinator]

Yaaayyyy.... well done. It is a great feeling when you fix something isnt it. I currently have gone the other way. Fixed something so much that it don't work. At all!
Your thread might just have convinced me to have a play with a v6 in the future.

[gryphon]

Jan 26, 2020 22:40:32 GMT procrastinator said:

Yaaayyyy.... well done. It is a great feeling when you fix something isnt it. I currently have gone the other way. Fixed something so much that it don't work. At all!
Your thread might just have convinced me to have a play with a v6 in the future.

It is! Was such a relief when I turned the key and it started properly (right after turning the key and realising I'd not plugged the cranks sensor back in)

Best of luck unfixing your fixed thing to fix it 

I thought this thread was more an advisory against V6s at this point...

[stealthstylz]

Great that you've got it fixed. Shouldn't have hurt anything.

[coskev]

Great thread👍

I'm running a AJ30 in my kit car,coupled to a RX8 6 speed gearbox.

Really pleased with the engine👌

I'm running a ST200 mondeo upper inlet manifold,mated to the AJ30 lower with some alloy spacer plates I've made.

Running MS ECU using a Mondeo wasted spark coil pack with custom leads.

We've altered the VVT on and off points,as the standard Jag VVT came on at 5200rpm,and stayed on to the rev limter.This actually reduced the engines power output at higher revs!

Mine now comes on at 1800rpm,and goes off at 5800rpm.
Power is still climbing at the 7100rpm rev limiter and it made 286bhp😎

[flyingphil]

Well Done - sounding sweet!

[goldnrust]

Woo! Thats good news I'm glad you got to the bottom of that one, was a tricky one for sure!

[gryphon]

Thanks all - and thanks for the advice along the way!

Now I just have a bit left to do for the MOT, mostly just bleeding things, tracking and front panels I think... I'm sure more will crop up though. Rather looking forward to getting this on the road.

My ordered wings fell through. Not entirely sure of the whole story, but after waiting two months the seller said they were posted, wouldn't give me a tracking number and immediately offered a full refund when they didn't arrive. Suspicious, but he followed through with the refund then promptly disappeared from facebook.
Instead I picked up new wings and bumper from a guy breaking one locally that had recently been resprayed. Not the best paint job, but in far better condition than my current ones and rust free. Unfortunately it will be the weekend when I can finally check them in daylight and probably find that they don't match the car in the slightest.

Jan 27, 2020 16:59:49 GMT coskev said:

Great thread👍

I'm running a AJ30 in my kit car,coupled to a RX8 6 speed gearbox.

Really pleased with the engine👌

I'm running a ST200 mondeo upper inlet manifold,mated to the AJ30 lower with some alloy spacer plates I've made.

Running MS ECU using a Mondeo wasted spark coil pack with custom leads.

We've altered the VVT on and off points,as the standard Jag VVT came on at 5200rpm,and stayed on to the rev limter.This actually reduced the engines power output at higher revs!

Mine now comes on at 1800rpm,and goes off at 5800rpm.
Power is still climbing at the 7100rpm rev limiter and it made 286bhp😎

First post! Thank you Interesting info too.

From what I can gather that's a rather good output, especially with the ST200 intake. Apparently Jag didn't make particularly good use of the CVVT either - second hand information, but Rocketeers initial plan was to copy the Jag implementation, only to find on the dyno, watching it with an oscilloscope it barely did anything. Many reasons why that could be in reality, but interesting none the less. I believe my ECU makes much more use of it but they are (somewhat understandably) coy with the details.

On the VVT engine Jaguar are very open about how they use the VVT, and that it's designed to be operated in conjunction with the original variable length intake system:

Far more information in this document. (Makes an interesting read, although much of it is no longer applicable to our ones)

What kit car is it in?

[coskev]

Jan 27, 2020 21:04:27 GMT gryphon said:

Thanks all - and thanks for the advice along the way!

Now I just have a bit left to do for the MOT, mostly just bleeding things, tracking and front panels I think... I'm sure more will crop up though. Rather looking forward to getting this on the road.

My ordered wings fell through. Not entirely sure of the whole story, but after waiting two months the seller said they were posted, wouldn't give me a tracking number and immediately offered a full refund when they didn't arrive. Suspicious, but he followed through with the refund then promptly disappeared from facebook.
Instead I picked up new wings and bumper from a guy breaking one locally that had recently been resprayed. Not the best paint job, but in far better condition than my current ones and rust free. Unfortunately it will be the weekend when I can finally check them in daylight and probably find that they don't match the car in the slightest.

Jan 27, 2020 16:59:49 GMT coskev said:

Great thread👍

I'm running a AJ30 in my kit car,coupled to a RX8 6 speed gearbox.

Really pleased with the engine👌

I'm running a ST200 mondeo upper inlet manifold,mated to the AJ30 lower with some alloy spacer plates I've made.

Running MS ECU using a Mondeo wasted spark coil pack with custom leads.

We've altered the VVT on and off points,as the standard Jag VVT came on at 5200rpm,and stayed on to the rev limter.This actually reduced the engines power output at higher revs!

Mine now comes on at 1800rpm,and goes off at 5800rpm.
Power is still climbing at the 7100rpm rev limiter and it made 286bhp😎

First post! Thank you Interesting info too.

From what I can gather that's a rather good output, especially with the ST200 intake. Apparently Jag didn't make particularly good use of the CVVT either - second hand information, but Rocketeers initial plan was to copy the Jag implementation, only to find on the dyno, watching it with an oscilloscope it barely did anything. Many reasons why that could be in reality, but interesting none the less. I believe my ECU makes much more use of it but they are (somewhat understandably) coy with the details.

On the VVT engine Jaguar are very open about how they use the VVT, and that it's designed to be operated in conjunction with the original variable length intake system:

Far more information in this document. (Makes an interesting read, although much of it is no longer applicable to our ones)

What kit car is it in?

Wow that's a interesting picture,I'll have read of the link thanks!

It shows that the VVT operates opposite to what I was told,as the VVT just advances the inlet cam by 10 degrees,so for that to be saying its retarded above 5200rpm,would mean the solenoid is activated at 1000rpm to turn it on.
Doesn't seem right somehow for VVT?

My kit car is a seven type car,so looks like a Westfield etc.

The ST200 inlet being a restriction is a myth!
Well I've never seen any proof that is a restriction.
Two of us now run the St200 inlet on AJ30's in kit cars,the other one made 276bhp,hence whe the ST200 inlet is not a restriction!

Mine made 264bhp with the VVT unplugged on initial mapping.
So I don't believe the figures to be wrong,as it's on tubular manifolds, no cats,open air filter,6.3kg flywheel, no PAS/aircon/water pump being driven.

How did you get on shimming the solid lifters?
Did you need to buy any shims to get the clearances correct?

[coskev]

That's a fifth gear pull hitting 141mph at the limiter 😎

[gryphon]

Jan 28, 2020 9:00:56 GMT coskev said:

Wow that's a interesting picture,I'll have read of the link thanks!

It shows that the VVT operates opposite to what I was told,as the VVT just advances the inlet cam by 10 degrees,so for that to be saying its retarded above 5200rpm,would mean the solenoid is activated at 1000rpm to turn it on.
Doesn't seem right somehow for VVT?

My kit car is a seven type car,so looks like a Westfield etc.

The ST200 inlet being a restriction is a myth!
Well I've never seen any proof that is a restriction.
Two of us now run the St200 inlet on AJ30's in kit cars,the other one made 276bhp,hence whe the ST200 inlet is not a restriction!

Mine made 264bhp with the VVT unplugged on initial mapping.
So I don't believe the figures to be wrong,as it's on tubular manifolds, no cats,open air filter,6.3kg flywheel, no PAS/aircon/water pump being driven.

How did you get on shimming the solid lifters?
Did you need to buy any shims to get the clearances correct?

To be honest I don't think I could say what sounds 'right' with vvt... The jaguar document does give a good detailed description of it though. Also, Supposedly 30* rather than 10*

Certainly looks like you're right about the ST200 intake... I was also under the impression it wouldn't fit under my bonnet, but it looks pretty compact on yours. Mine has a cat and a PAS pump to drive, but should make around 270 in theory.

I measured the valve clearances, most were in spec, a couple slightly out but not enough out to warrant me buying the tool to change them or taking the cams out again! Annoyingly I didn't note the measurements...

Your car does look great fun.

___________________________

In other news, did I say my new wings were rust free? I need glasses.

On second inspection of the normal rust points for MX5 wings - front corner of the wheel arch and bottom over-sill section - there was definitely rust on the inside that had been quickly sprayed over with colour. Oh well, out with the angle grinder. Metal is pitted, but no holes, and I guess I'll be able to test the Bilt Hamber stuff after all!





And followed by two generous (and not very neat) layers of Hydrate 80...




As I still don't have the right PPE, and I'm not a masochist, the epoxy mastic tins are staying firmly closed. I'll just be giving the wings a coating of Dynax UB in the rust prone and impact areas, and a spray of Dynax S50 elsewhere...

[gryphon]

Feels like a lot of time was spent on the car over the weekend without all that much to show for it...

Finished off the wings:

And fitted them to the car, along with the new front bumper. New bumper is from an Eunos, and since being sprayed has had the Eunos badge re-fixed with some stubborn glue. I'd prefer to have the old Mazda badge but don't want to risk the paintwork!

Clutch bled. Front brakes bled. More things reattached, wheels back on and we took it for a sneaky up and down the street... Not that there's much sneaky about the exhaust...

On Sunday I broke out the cleaning supplies, hose pipe and polisher and got to work. Most of a day spent cleaning and polishing a car is not my favourite use of time, but the paint was looking pretty pink, and the roof had rather more green stuff starting to take root in the fabric than is proper.

After a fair few passes with the polisher even the rattle canned rear arches were looking passable from a couple of meters. The rear bumper on the other hand is quite stubbornly pink and needs some more attention.

But then - as I keep reminding myself - it only has to look passable. I don't want a show car, or even for it to stand out too much - which it definitely doesn't at the moment!

^Need to fix that nearside headlight cover...

Unfortunately a weekend MOT is looking less likely though as it's now got a bit of a (suspected) vacuum leak making the idle rather erratic, especially if the brake pedal is pressed. Don't hear about the servo diaphragms failing often, but that's my first guess at the moment. All my earlier testing with the engine was done with the servo disconnected and it was running nicely!

I'll also be loosing the nice Konig wheels as my 5 spoke enkeis are having some newer tyres swapped onto them. When I swap the rears I'll raise the rear ride height about 10mm to bring it in line with the front too.

[gryphon]

Where to start... Ah yes - excuses. Weathers been dreadful and life has been busy.

No MOT yet but little bits here and there have been happening

First up, a downgrade.

The good tyres got swapped onto the enkei alloys (OEM from an NB MX5) and I swapped them onto the car. I like the look of them, but the fitment looks rather weak, they sit a little too far inboard for my liking. I do much prefer them to the TRWs that came on the car though!

Once the tyres were off I could finally sell the TRWs. Popped them up on FB and have never had so many timewasters from selling anything before! After 4 people arranged to collect and then ghosted me I finally got a legitimate buyer - turns out he didn't actually want the wheels, they were going in a skip but he wanted the centre caps, clips and plastic spanner from them for a 17" set he has on a 600bhp Sierra Cosworth. It hurts a little chucking a set of wheels that actually cleaned up pretty nicely in the skip! Ah well, not mine any more.

At the end of the last post the exterior of the car was looking pretty tidy, but after the various stripdowns and diagnostics the engine was looking pretty messy, especially the wiring harness which was all over the place.

I got some harness tape, and tesa cloth harness wrap and set to work.

   

The back of the engine bay is still a mess, but the most offensive bits have been dealt with!

The rusty battery tray in the boot got zinc primed over the hydrate 80, then a layer of colour:

Much improved, and I fitted the original mx5 'lightweight' battery, vents plumbed in and all... Only to find that it really didn't like cranking the V6, it didn't even try! I knew it wasn't the most healthy battery, but it had cranked the old 1.8 very happily when I was playing with the supercharger and failing to start it on the MS2 ECU. Oh well, I'll keep stealing the Porsche battery!

Next I found a little time to fit the front numberplate and front bumper grille. I didn't like the big plastic plinth that the plate sits on from factory and went with a JDM style bracket that bolts onto a towing eye. It's designed for a square import size plate rather than a UK one, but the UK one is bolted on for now and actually doesn't look as bad as I'd expected.

I spent an evening on MOT checks lights, washers, horn etc and was happy to find it all working - or at least it was all working until I gave the indicators a final flick, at which point they decided to indicate left all the time. Felt like a stalk switch issue as there was a very small area in the switch where I could actually turn them off... so off comes the steering wheel again:

The first thing I noticed was that the ring around the steering column that does the self canceling is cracked clean through near the stalk mount. This doesn't have much effect on the indicators, but is the reason the full beam/flash action on the stick felt rather sloppy. Dismantling it to try and fix it resulted in me breaking it even further... So need to find a replacement! I've done a messy epoxy fix that will hold in the mean time though.

Back to the actual problem I wanted to fix, it was just dirty contacts on the switch. A wipe over with brake cleaner then a scrub with a glass fibre contact cleaning pen did the job. Old left, cleaned right:

 

Reassembled with a little PTFE grease as my pot of dielectric silicone grease has gone walkies.

Seemed reasonable to check the wiper switch while I was there - despite working fine it looked even worse! Before and after again:

And again reassembled with a little fresh grease.

Everything back together and lights are MOT worthy once more

A while back in the thread I mentioned that I was on the lookout for a set of OZ Superleggera wheels... well naturally as soon as I'd got the Enkies swapped on a set popped up on ebay. I missed the last set 6 or so months ago so bit the bullet. Seller was very helpful, shiply courier rather less than helpful but they arrived eventually.

Ooh Shiny!

I want to do a before/after drive to see if I notice the difference with the lighter wheels so not fitting them quite yet, couldn't resist a test fit though. A quick check shows the Supers are 2kg ligher each. (12.9kg vs 15.1kg - obviously there will be differences in the tyre weights too though)

The enkeis are 15x6.5j et45 and the OZ's are 15x7j et37 so if my understanding is right they should sit just over 14mm further out. (1/4" + (45-37)mm). I didn't try to measure it but they definitely look better. (OZ left, Enkei right)

  

Turns out I'm rather glad I did the test fit... With the wheel off I could see that the polubushes were busy removing themselves from the upper wishbone!

Looks like they need a big penny washer to hold them in place. They didn't have any when I removed them from the car and I've no experience with polybushes so hadn't realised anything was missing. I think the original subframe did a better job of holding them in place than the rocketeer one which made the issue less obvious. One more thing to delay the MOT until the washers I've ordered arrive, I really had hoped to get it all prepped this weekend. Now I'm writing this post as procrastination for CADing up the panel to hold the screens beneath the radio... But I've run out of things to write about, so back to CAD it is!

[goldnrust]

Eeek! That polly bush is a bit scary! Good that you spotted it. If I remember rightly, the standard subframe has a reasonable lip there, that the bush can push against. Possibly another ne of those extra details which the Rocketeer kit seems a little light on.

New wheels look cool, though I have always had a soft spot for the OEM Enkeis, I ran a set in white with 25mm spacers behind them on my Mk1. The 25mm spacers made quite a difference to the look of them.

[gryphon]

Mar 15, 2020 20:08:29 GMT goldnrust said:

Eeek! That polly bush is a bit scary! Good that you spotted it. If I remember rightly, the standard subframe has a reasonable lip there, that the bush can push against. Possibly another ne of those extra details which the Rocketeer kit seems a little light on.

New wheels look cool, though I have always had a soft spot for the OEM Enkeis, I ran a set in white with 25mm spacers behind them on my Mk1. The 25mm spacers made quite a difference to the look of them.

Yeah, very glad I spotted the polybush - not least (safety aside) because I'd have turned up to the MOT station where I have a good rapport with the tester an immediately looked like a complete idiot! The stock subframe does hold the bush on better but after googling all the polybushes come with penny washers to keep them in place properly. I'll chalk this one up to the PO!

I like the OEM Enkeis too, especially in white - best 15" OEM wheel imho, and amongst the lightest 15"s too. 25mm spacers would improve the appearance too, but I primarily went with the OZ wheels for the lightweighting. They are marginally heavier than Enkei RPF1s and to get any lighter again they have to be forged... I've currently got it in my head that I want light wheels, part of the reason I want to do a back to back drive is to see if I do actually notice the difference or if I've just got hooked on an idea.

[goldnrust]

I definitely felt I could feel the difference between the lightweight OEM Enkeis and much heavier Rota wheels that were previously on my Mx5, but that was probably a bigger difference that the Enkei to OZ weight? I agree that running without spacers is better, and also lighter if that's the goal

And yes white was the best colour for those OEM Enekis (I say this because mine were white!)

[gryphon]

Only a 2kg difference per wheel (with current tyres) so not a huge difference. Will be an interesting test. My gf is far more likely to pick up on the difference than I am so I'll ask her to A/B it too!

Weren't the White Enkeis part of a J only track edition car?

Shamelessly stolen photo from google images:
Edit: Photo here, I realised I was shamefully using up somebody elses photobucket allowance

Does look good red on white... needs the spacers though.

[trimtechniques]

What a magnificent project. I also have a Dakar MX-5 and you have got my mind turning over what is possible. Mind you thinking about it and doing it are Two different things.
I admire your resolve and tenacity.