1978 Fisher Fury - whoosh!

[mylittletony]

Seeing as it's rained almost constantly for the past week, I decided to crack on with extending the bottom flange (snigger)

First step was to sand back the edges, which I just about managed with a very cheap new mini grinder.

Then mask off the car



Then a couple of layers of parcel tape, ready for resin



Then 1 layer of glass, followed by a second more localised layer, around the edges and across the back



Not my finest work as I discovered once I'd started that my roller was seized...

I'm going to try and use it this week as the forecast is dry, then probably get stuck into building the form

[mylittletony]

Mini-update, mainly as it's been a month since my last post!!

The adjusted wastegate actuator was still allowing nearly 12psi, which according to the chap doing the tuning is fine for a std MX5 engine, but not for the injectors I have fitted.

Here's me testing the actuator as scientifically as I could think of



Not really wanting to cough up on a set of bigger injectors and also because it's pretty f-ing fast as is, I plumped for an adjustable actuator to bring the boost down to within the fuel system capacity. I also discovered the position of the actuator can was causing the movement of the arm to be obstructed.





The new actuator is a cheap one, similar to a mambatek, supplied with springs of different ratings. I've fitted the 0.3 bar spring to see where we get to. I took the opportunity to lower the actuator body, away from the bonnet, and made a cranked actuator arm to make sure the motion is smooth.





The result of this, after a few data log drives, is that I'm seeing 4psi at ~5k rpm, but it's rising fast. Next step is full throttle up to 7k - that's proving hard with how wet it has been and how damp the roads are!!

Once that's all bottomed out, I'd like to increase the boost until I get around 8psi.

Other fantastic news to report is that it starts brilliantly from cold and is driveable immediately - the initial goal from this whole malarkey!!

[DWDarkWheels]

Interesting work on the hardtop. I never realised such a thing was available for these but always liked the idea of these sort of cars made into a sleek coupe. That original top is anything but sleek so I wish you luck transforming it.

[mylittletony]

Thanks!

The hardtop has taken a back seat, I've been out round the block a couple of times to get this tune sorted so the bits haven't been on the car for a while. As the weather gets darker and wetter I'm sure I'll get into it again. There's another reason which I'll get to in a minute!

As for the tune, I got up to 7k revs, but the boost was climbing and climbing so something wasn't right.

I checked the wastegate actuator and it opens under a whiff of pressure from the bike pump, so that's working.

I started to wonder about an exhaust restriction and then the tuner mentioned bad wastegate port shaping, especially with the Chinese stuff. This would definitely describe my symptoms, the wastegate can't actually dump exhaust gases, so the turbo keeps boosting.

I checked my old turbo



Big flap, small hole, doesn't look very promising, hmmm.

Then in a flurry of activity, I removed the turbo and split the turbine housing off.

Same deal



And from the other side



So the plan is to open the hole up a bit and blend the entrance side to ease the flow for the exhaust.

Hoping I can have it back together fairly quickly!

The other reason I've been distracted, and not bought materials for the hardtop, is I've bought another car and marginally overspent! It needs some weld repairs and a few other bits buying, although I'm hoping I can enjoy as is over the winter

I'll start a thread soon, but ultimately, this may get sold to fund a build...

[mylittletony]

Time for some 'after' photos.

The housing was attacked with the following implements, all found in my messy garage: 18mm drill bit, cheap burr tools, round hand file.






I have smoothed the edges since taking the pics.

I'm calling that a success, going from 15 to 20mm diameter virtually doubles the area and the blending is significant, even if you can't see it in the photos.

EDIT, check out my editing skillz, a little side-by-side



I've put the turbo back together, after a thorough blow out, but not refitted to the car yet.

Can confirm I do have black bogies after all the grinding.

[mylittletony]

To continue the story, in short - Success!!

I refitted the turbo and actuator etc, this time adding a couple of mms of pre-load. I've just come back from a test-drive, the usual story of family logistics and weather conspiring to prevent this any sooner.

I thought I would demonstrate the issue with snips from the data logs. Here's the previous log full throttle pull, the 'before' porting condition.



The green trace is throttle position, the white is engine speed and the red is Manifold Air Pressure, which you can see is all over the place. The main point is that it keeps climbing all the way to 180kPa, which is 26psi, or 11.5 over atmospheric of 14.5 (Confession time, I have not taken into account exact atmospheric pressure for this post)

Now you've all digested that, here's the same pull on the same stretch of road, after porting the turbo housing.



Green and white lines are similar, except you can see I bottled out of a full throttle pull.

You can see the MAP plot jumps up, then is broadly flat at 122kPa, which based on the same calculations is 3psi boost. However, most importantly it is NOT rising with engine speed.

So yeah, it worked!! Success!!

Now I have some control on the boost, I can look at increasing it back up to somewhere like 7-8psi. And I don't have to take the turbo off again!! lol

[mylittletony]

Quick note for bstardchild as I've seen you liked the previous post - I think the noise issue was the car hitting boost cut rather than a limiter, and I didn't have a great amount of control over it!!

I'm very confident this tuning will make the car less savage but still plenty fast!

[mylittletony]

Here's a little step by step of swapping the springs on the actuator.

Clamp in the vice while removing the screws



This shows the internals. A simple plunger, diaphragm and a spring.
Change the spring, change the pressure required to move the plunger and open the wastegate.



Here's the range of springs it came with. I've swapped the 0.3 bar for a 0.5 bar one, should get 7-8 psi instead of 3-4.



All refitted now, next thing is a datalog to check fueling.

[mylittletony]

I managed to get out for a lap yesterday late morning which showed the new spring does its job!



The peak MAP is now 149kPa. The MAP before starting was 99kPa so I achieved exactly 50kPa or 0.5 bar boost.

Somewhat interestingly, the boost pressure tails off a little, which we think might be attributed to the wastegate feed coming from the compressor housing and the sensors reading from the manifold. However, if I fix that I'm told I'm out of injector again!!

Virtually all comparisons I can find are that 7psi on a mk2 MX-5 gives 200rwhp. It's back to being super fast, but now I can rev it out to 7k without it cutting/limiting - it's brutal.

I've got a final tweaked tune to load up and test, then just drivability feedback - but tbh it's really rather nice compared to how it was!

[Blown_Imp]

Just catching up on this one Tony; ace news that the smoke was the turbo and not the engine.

What is this winter beater you mentioned?

[mylittletony]

It's dawned on me I've not mentioned who has been doing the tuning work on the car...

I was recommended to call Tom at Coldside Engineering www.coldsideengineering.co.uk as he a lot of experience tuning forced induction MX-5s with Megasquirt and Speeduino using Tunerstudio. I had some reservations as he is not local to me, so it would be remote only. I also thought (naively) that the tune just needed a tweak as it drove "well" once up to temp.

However, as my posts have hinted from start to finish he's been excellent! I would highly recommend him to anyone and in fact considering basing my next build on the same tech so I can use him again!