Mx7? rx5? Newbies build thread begins

[Steve-A]

Well its been a few weeks. Working, a small holiday and difficult times with my girl friend  ( ) have got in the way of the car.

Yesterday morning I was finally able to goto the post office to pick up my oil cooler. Heres how she looked, a little rough around the edges but non leaky!



So I gave it a quick cleaning up, didn\'t have any high temp silver paint left so was just solvents and a bit of gentle wire brushing and then fitted my brackets.



And chucked it in the car. Ran it up and all seems well, I\'ve done 150miles since yesterday morning and so far not a hint of oil seepage



I also realised my slow coolant loss could well be down to having two pressure caps in the system, and that only one was connected to the expansion tank. My two caps were 1.1 bar and 0.9 bar and the 1.1 was on the expansion tank. For the short term I\'ve swapped the caps over and so the lowest pressure is now on the expansion tank. I\'m gonna get on and find a fixed cap for the filler asap



Its been lovely to drive the car again I had an awesome drive today, 10 miles of b roads never letting the revs drop below 4k. It may have used a stupid amount of petrol but its made me smile more than anything else has for the past fortnight. I\'m so glad I managed to go through with it and complete it.

It got washed this morning, I have friends who have VWs who are more into washing and polishing than I am, so it even got dried properly and the faded bumper got waxed. Its an odd feeling having a clean car! Will try and take some pictures tomorrow.

[captainbizzaro]

Good work!

[Steve-A]

Cheers Right now being able to drive it is really cheering me up

The only downside is I\'ve spent £40 on petrol this weekend, and only done 150 miles or so. :o Heres the pics I mentioned yesterday, not the best weather but the car is unusually clean so seemed a good idea to document it!

[Steve-A]

Few of the guys on the mx5 forum were after another vid of the car now its running properly. Heres a quick clip of the car driving up a local road. The proper video I\'d like to make of it will have to wait a few months so i just got my sister to hold a camera. She was struggling a little with the bumps!

Either way you can hear the exhaust well, if not the pops and bangs on over run so well. They are there but sound more like one of the many interior rattles!


http://www.youtube.com/watch?v=RDK7GF5rgP4

[marcusd666]

its looking really good steve was good to see it in the flesh at rotorstock and meet yourself and chat. If idi not have my FD3 i think i would go this route with the rotary you have done a really good job.

[Steve-A]

New toy!




I\'ve been thinking about buying one and learning to weld for quite a long time. So I thought I\'d bite the bullet as my sills will need work in the no so distant future, and there\'s that small hole in my frame rail and I need to work on the diffuser design for my exhaust.

Heres how the diffuser stands right now:




This definitely makes a difference to the drone, if not the overall volume. I think the key is using the restrictions to break up the gas flow into high and low pressure sections then it will tumble and will break down the harsh pulses the rotary engine creates.

I\'ve still a long way to go before my welding is good enough to weld anything that matters/need to be strong so I\'m trying to find things to do to practice. Thought I\'d play with some thin stuff so made my girlfriend a metal butterfly this morning.



On the whole the car is just working as it should beside the speedo not working yet. I\'ve done lots of miles and I\'m enjoying thrashing it and still concerned about the fuel economy!

[Nik da Greek]

http://www.youtube.com/watch?v=FD-0dfhAgAU

Cool butterfly, dude :Giggle Reminds me of when I was doing my chainsaw training and we used to have to carve little chairs and stuff out of logs to get the fine control sorted. Except mine never seemed to end up with legs the same length :o

[rossonza]

haha thats ace Steve!! i happen to know a fellow who requires some welding work doing........

[shaunwil]

Very cool butterfly. I have welded my exhaust up more times I can mention on the fb !

Shaun

[Steve-A]

Gonna need a hell of a lot of practice before I\'m ready to face your rot box Ross

[Steve-A]

Been doing some research into why my car is chewing up speedo drives. I\'ve found this highly useful website: http://www.solomiata.com/Drivetrain.html

Judging by the gear ratio chart, and how the revs match the speed of the rx7 box vs my mx5 box I\'d say I\'ve not got the s4 box I thought I had but likely a s3 box. Which would explain why 5th isn\'t as long as I had hoped it might be.

It would also explain why I\'m chewing up speedo drives. All mx5s and s4/s5 n/a rx7s should have interchangeable speedo drives just with different gears on them to account for different ratio diffs. The s3 box has a different tooth pitch on the speeod drive to all the others. So I\'ve posted a wanted thread and I\'ll keep my eyes open. If anyone has a 17 tooth speedo drive from a s1, s2 or s3 fb gearbox I\'d like to buy it off you!

If I cant get the right speedo drive I will have to rebuild the box with the mx5 gear on the tail shaft so I can use an mx5 speedo drive. The actually gearbox rebuild section would take 20 mins, but I fear due to the way I\'ve shoe horned the gearbox into the car I\'d need to remove the entire exhaust system, to remove the exhaust I need to disassemble the entire intake assembly, the whole front suspension assembly will have to be removed so the front subframe can be dropped so the engine can be swung forward, which means removing the rad and oil cooler to make room to swing, so I can get to the gearbox off the back of the engine, clearing the clutch.

Not cool!!!

I\'ve been thinking about my exhaust diffuser too, whilst cutting the drone is has resulted in quite a \'blowy\' kinda sound to the exhaust, especially at low revs. The diffuser seems to be working by breaking up the exhaust path so the harsh pulses of sound don\'t hit the end of the exhaust so cleanly. Which got me thinking. Tonight I\'m going to try and weld up an extension to the exhaust tip with a 30 degree or so angle to it, downward pointing, which firstly should add more tumble and disturbance to the exhaust flow breaking up the pulses and secondly point the sound at the floor to dissipate rather than up into the air behind the car. I will then slash cut the end of the 30 degree section so once again the exhaust pulses don\'t hit such a definite end to the pipe. Hopefully that will further help take the edge of my exhaust.

If the car was a hard top then i\'d say its currently acceptably loud but with the roof down cruising its just still a bit harsh.

[kiwimazda]

Back to the oil cooler issue.
I ditched my mazda ones years ago and went for Mocal. Never ever have I had a problem and they were to  find some one for testing them for vibration then I am the man with the amount of "off road" excursions i have had

[Steve-A]

Thanks, worth knowing for the future.

For the moment my temps seem well under control and there\'s no sign of any leaking from the new cooler.

Why didn\'t I buy a welder sooner, its soo much fun/so useful.

Tonight I further modified my exhaust tip to have a downward slashed tip. The result is no real reduction in volume (I wasn\'t expecting any) but it has taken some of the hashness of the sound, making it smoother and easier on the ears. The proof will be in tomorrows commute!




Also having posted in the mapping thread I\'m gonna play with my trailing split tomorrow and see how that goes.

[Steve-A]

Speedo drive is in the post

I\'ve had a play with the trailing spark advance and its really transformed the drivability of the engine. Its much smoother on cruise and now runs out of puff at 8,100 rpm rather than 7,700 rpm  :popcorn:

Unfortunately there\'s a black cloud kinda hanging over the car right now I\'ve been doing some maths and as my daily driver, doing the amount of millage I\'m now regularly doing petrol is gonna kill me . Most of my friends live 25 miles away, as does my girl friend, and my main client is 50 miles away. This all comes down at 500-600 miles per week, and quite possibly £4-500 per month in petrol which is a bit ridiculous.

I knew the fuel economy would suffer when I started this but sometimes my heart just runs away with me! It lied to me and told me I could afford it  :paperbag:

I cant carry on like that, so somethings gotta change. There\'s various options I guess.

I could buy a daily driver and keep the rotary 5 as a weekend toy. This would be good as I\'m so pleased with how the 5 has turned out and I\'ve put so much of my heart and soul into it. The main downside is that I\'ll be doing many many hours in the daily so really would like something economical, with a nice driving position, fun to drive at low/standard power and really Id miss my soft top on the commute if I went for tin top. I think its fair to say I\'m pretty much describing a 5 there! but I don\'t want two cars practically the same.

I could sell up the rotary 5 and buy another turbo 5, back to 40mpg on the cruise and 200+hp at the right foot when wanted. Good in terms of money. I\'ve become really attached to these roundy-roundy engines though, they feel some awesome when thrashed! The other main downside is that my project car would once again be my daily. Doing the rotary swap I\'ve noticed how in a way I enjoy playing with spanners as much as I do driving, and when taking on fairly big modifications its a real pain to have to always have the car back together in time for work.

I could sell the rotary 5 and buy a standard mk1 to daily drive then have a different project car. This way I could have all the fun of the 5, and the soft top, for normal use and the project can be really impractical and wont matter if its a tin top. I\'d be very tempted by a 1st gen Rx7 so I could retain the rotary awesomeness. And if I bought a ratty one it would be a good project to get stuck into. On the other hand I\'ve wanted an Alfa 105 chassis coupe for a very long time, and that HAS to be a 2nd car which is why I\'ve always discounted it. On the downside I\'d have to insure/tax/maintain two cars.

I really don\'t wanna let go of my rotary 5 but at the same time I don\'t wanna be driving a crappy euro box most of the time and I cant afford £500 a month on petrol!


Either way I\'ve still got finishing touches to do on this 5 and I don\'t think this decision will be made lightly so not gonna rush it.

[Steve-A]

Well I\'ve got round to posting my v5 off to the DVLA with the new engine number, and I\'ve got new copper washers for the oil cooler to stop it weeping in the post and I\'m working towards finishing the car. Whether I keep it or sell it I could do with a final push to finish the last few niggles.

Yesterday afternoon I attempted to fit the speedo drive that was very kindly dug out for me. Unfortunately when I took the old one out I was greeted with this sight:



Thats the speedo gear inside the box being split in two. Bad times. Gonna need to get the box apart to fix that. will think long and hard about the best way to do that. Part of me thinks I might be able to unbolt the prop from the diff, then drop the back of the box down and remove the tail section while the front section is still bolted to the engine and in the car. If there is enough room to do that it would be by far and away the easiest.

I don\'t know why the speedo gear is split, nor if that has been part of the problem all along, nor if its me putting the wrong speedo drives in there that has cause the gear to break. Either way the best thing, and only thing, to do now is to put an mx5 gear inside the box from my spare gear set and then use a standard mx5 drive too.

I also had a go at my frame rail repair.




Here I\'ve cut out the rusty bit where the two section of rail join. I made a small patch and welded it in. I spent quite a long time practicing with the same thickness of metal and my welder making sure I had it set just right to get good penetration yet not blow holes. I wanted this to be neat.



Thats the end result. Not neat As soon as I\'d tacked it in it started blowing holes. I don\'t know if the chassis is made of steel blend that melts easier than my repair metal or whether it was just my shoddy torch control from lying under the car. Its done though, its plenty strong, just not very pretty. I then chucked some under seal on it and went out for the night!