Mx5, Chapter 2

The American · Postby **The American** » Mon Aug 04, 2014 7:37 pm

It's been a long time since my last post in this thread. I've since been introduced to the joys of malfunctioning boost control and some over boosting, although it took me a while to work that out.

After working through simple things like plugs and leads, and checking for vacuum/boost leaks, I put a boost gauge on the car and discovered the problem. When switched to 'low boost' the car runs fine and holds a steady wastegate pressure. When switched to 'high boost', the boost pressure flys past the target pressure, and (from my limited understanding) past the limits of the fuel map...

The ECU in the car is a piggy back system supplied by Mx5mania some years ago and it is no longer supported by them or the original maker, who has apparently passed away. RIP. The ECU should be controlling the MAC boost solenoid to limit boost to the target, but it's not working. I've replaced the solenoid, and rechecked wiring to no avail.

In any case, the over boosting issue is now beyond my knowledge/experience to solve, and to do anymore than I have now, would simply involve replacing sensors, on an almost random basis. I thought it might have been the map sensor, but then it runs fine on wastegate pressure. It could be the driver for the solenoid in the Piggy back, and it's beyond me. I'd love to find the fault and fix it myself, but I'd love even more not to detonate my engine!

Allstar Tuning in Brendale have previously tuned this car for the last owner, but contact with them has been unresponsive. I've heard good things on his forum and elsewhere about GT Auto Garage, but they are not able to work with my ECU arrangements!

So, here comes a visit to GT Auto Garage, a Haltech, and a fresh tune.

Magpie · Postby **Magpie** » Mon Aug 04, 2014 7:44 pm

GT Auto Garage if Danny puts his faith in them so can you plus they tune my car as well.

Check with Lokiel as he may have some other suggestions like Adaptronic as this is what he is using.

The American · Postby **The American** » Mon Aug 04, 2014 10:51 pm

yes, they certainly seem well-reviewed on this forum. I've been following Danny's build. Some beautiful engineering and design.

The American · Postby **The American** » Thu Aug 21, 2014 10:30 am

There was an old Mx5 that swallowed a piggy back. I don't know why it swallowed a piggyback, perhaps it'll die.

There was an old Mx5 that swallowed a Haltech, it wriggled and jiggled and emptied my wallet. It swallowed the Haltech to catch the piggy back, I don't know why it swallowed the piggy back. Perhaps it'll die.

There was an old Mx5 that swallowed a flex sensor. What an expense if you want to flex sense! It swallowed the flex sensor to support the Haltech, that wriggled and jiggled and emptied my wallet. It swallowed the Haltech to catch the piggy back, I don't know why it swallowed the piggy back. Perhaps it'll die.

There was an old Mx5 that swallowed 1000cc injectors. Almost certainly overkill, such big injectors! It swallowed the injectors to flow E85, through the flex sensor, to support the Haltech, that wriggled and jiggled and emptied my wallet. It swallowed the Haltech to catch the piggy back, I don't know why it swallowed the piggy back. Perhaps it'll die.

There was an old Mx5 that swallowed a Walbro. To make it go, it swallowed a Walbro! It swallowed the Walbro to feed the injectors, to flow e85, through the flex sensor to support the haltech, that wriggled and jiggled and emptied my wallet. it swallowed the Haltech to catch the piggy back, I don't know why it swallowed the piggy back. Perhaps it'll die.

There was an old Mx5 that swallowed a fuel reg. should'a bought some sticker bling instead! It swallowed the fuel reg to control the Walbro to feed the injectors - Almost certainly overkill, such big injectors! It swallowed injectors to flow E85, through afore said flex sensor, to support the Haltech, that wriggled and jiggled and emptied my wallet. It swallowed the Haltech to catch the piggy back, I don't know why it swallowed the piggy back. Perhaps it'll die.

ManiacLachy · Postby **ManiacLachy** » Thu Aug 21, 2014 1:29 pm

Excellent post!

Though it sounds like you're having some issues, expensive issues, so maybe not so excellent after all.

The American · Postby **The American** » Tue Aug 26, 2014 3:14 pm

I called in to GT Auto Garage to check on progress, and had a brief chat with the Dave who will be tuning the car. He seemed to think that 185rwkw was optimistic!

AutomotivePlus have done the work to plumb in the HKS fuel regulator, modify the fuel rail to accept a return line and install the NB8A return line and cradle. The new pump and injectors are installed.

It will be a week until I can pay another visit. Hopefully by then, the new ECU will be in the car, a tune will be done or underway, and the hub dyno will reveal all.

And what a collection of cars is squirrelled away in those sheds!

The American · Postby **The American** » Tue Aug 26, 2014 3:19 pm

Here's a link to the last dyno sheet I have (from previous owner).

http://mx5cartalk.com/forum/download/file.php?id=11559

The American · Postby **The American** » Mon Sep 01, 2014 8:47 pm

I called in to GT Auto Garage this afternoon, and spoke with Dave the tuner. My car spent some time on the hub dyno today and now has a map for pump fuel and a map for e85.

On pump fuel at 12psi it made 160-something RWKW. On E85 at 14.7psi it made 191 RWKW.

No more hi/lo boost switch!

The cold start tuning and other fine tuning is still to be done. I'm definitely looking forward to taking it for a spin!

The American · Postby **The American** » Tue Sep 02, 2014 10:00 pm

I picked the car up from GT AutoGarage this afternoon and drove it home. No real opportunity to stretch it's legs in that distance, but there is certainly a little extra poke.

It starts and runs fine, and idles smoothly. The initial throttle response (the first touch) is better than it was with the old ecu. The power delivery feels much smoother. It felt much more "on/off" with the previous ECU.

The noise from the engine bay is different (not the induction or exhaust notes). I suspect I'm hearing the new injectors.

Hopefully I'll have some time to spend on a proper drive on the weekend.

The American · Postby **The American** » Wed Sep 03, 2014 7:55 pm

Here are the results of Haltech PS1000, fuel system upgrades and retune.

The American · Postby **The American** » Sun Sep 07, 2014 4:48 pm

I went for a drive over Mount Nebo this afternoon and returned through Samford. It's the first time I've been over that road in an MX5 and is was rather fun. Although, after the township it began to rain and the road became incredibly slippery. Even a small dab at the throttle in 3rd unstuck the rear. Consequently, the last 20km was at about 60km/h behind a suitably cautios 'p' plater in an 86.

I'm experiencing substantially more low rpm power with the new tune. On a dry road, pulling from low rpm in second, as boost comes on so does wheel spin. WOT is of no use in first gear , and passes the limits of street tyres in second. Is not really possible to explore third gear on the road.

My mind is now turning to the suspension and handling. The car sits on a set of Tein Super Street coilovers and uses the factory anti-roll bars. My old NA8 had some Circuit Spec coilovers and whiteline adjustable sways, and felt very 'chuckable'. By contrast, the NB has a lot more roll and feels less 'stuck on'.

I need to find some events to participate in, to start exploring the limits of what I've got now.

M1474 · Postby **M1474** » Tue Sep 23, 2014 11:02 pm

Great read, The A.

The B looks amazing in white.
Glad to hear you have the tune sorted, now to find somewhere to play!

The American · Postby **The American** » Tue Sep 23, 2014 11:35 pm

Absolutely!

There's a 'come 'n' try' day at the MGCCQ hillclimb course on 19 October which I've signed up for, and will be its first track outing since I've owned it.