Mx5 project log

saitrix

saitrix

saitrix

Soldato
Joined
2 Jun 2003
Posts
8,950
Location
Nottingham
Here is my log of work I am doing on the mx5. Now I decided I wanted a bit more power for not much money. Always good really, so the way to do that is to fit a 2nd exhaust cam on the inlet side. Got the cam for a nice £30 and people have found it to give 10bhp extra, as proven by dyno.

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First of all was to cut the cam angle sensor off the cams, as it is only used on the exhaust cam. Took a while with only using a junior hacksaw. :p

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Next thing was to take the rocker off, nice and easy job really. Just take all the bolts off and unbolt the coil at the back of it. This is what it looks like when you get it off.

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Now to get the cam gear loosened. That was real tight, but once off now there isn't that much more to do to get the cams off. Before taking the gear off I used a crayon to draw a line of TDC for both the cams, plus ziptied the exhaust side on. You also want to ziptie to keep the left hand side of the cambelt in place. Once done it should just slide off!

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Then to get the bearings off that hold the camshaft on, best way was to use a rubber mallet on them, got them off in the end. :p

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Now you can just put the other cam in and put it all back together with the correct timings. How I did it I think I might be slightly out timing wise as I haven't gained power at all, but will need to look into that more. Was fun anyways. :p Will keep this updated as I sort it out, right now I know I am not using 100% correct timings but I didn't expect such drastic power difference.
 
I will get power out of it, just needs timing sorting better when I got the tools to sort it properly. :) Just went for a proper drive and its fine if you keep it above 4500rpm, and it doesn't like going below 2500rpm. But it's perfectly drivable for now, will get it sorted in a week or two.
 
Right just a small update, redid my cam with proper timing and it is running perfectly again. :) Certainly has helped at high revs without losing any power at lower rpms. Makes the engine feel much more eager to rev, and with no drop off before the limit. Now I may have to up the limiter to get the maximum out of it...
 
saitrix said:
Right just a small update, redid my cam with proper timing and it is running perfectly again. :) Certainly has helped at high revs without losing any power at lower rpms. Makes the engine feel much more eager to rev, and with no drop off before the limit. Now I may have to up the limiter to get the maximum out of it...
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Changing the crystal in the ecu mod for RPM?
 
paradigm,

Need to get uni exams out of the way and working again, but I will. ;)

Firestar_3x,

Yep, the thing runs rich enough for it to be all fine just overclocking the ecu. Only probably up it from 6900rpm to 7400rpm.
 
Oh I have also fitted a k&n cone filter to replace the useless HKS one. It's bolted directly onto the MAF so it is much neater.

So far today I have ordered shorter MCU bumpstops, will give much more suspension travel. I have got myself a cabin brace, for some reason mine never had one. Finally I got myself a new shock top mount cover as you can see in the below pic is missing.

Also hopefully buying a mk2 front anti roll bar. I already have a thicker one than most mk1's (I have 20mm, mk1s normally have 19mm), the mk2 has 22mm. I am also going to hopefully order some custom springs too today, raise it up slightly and double the rate of the springs. Then I can also remove the rear anti roll bar.

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Yep I know! :p If I really could be bothered I could make a heatsheild for it, doubt it is really worth the effort though.
 
Will Gill said:
air filter right by the manifold

nice design mazda :p
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Jeez, that is a bad design.

I'd be looking into some heat shielding for that.

saitrix said:
Yep I know! :p If I really could be bothered I could make a heatsheild for it, doubt it is really worth the effort though.
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It will be worth it. The amount of power lost from sucking in all the hot air will be noticable. Seems pointless modding the engine to make more power when somehing so simple is robbing you a handful.
 
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Eek, that air intake is really close to the exhaust manifold though!! Not such a good design really compared to the mk2 onwards.

Fun little project, what else you got planned? :)
 
Firestar_3x said:
It did have an enclosed airbox before he fitted a Chav Cone :p
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Hey my car came with the JDM tyte filter!


Freefaller,

First of all sort out my suspension properly, it is running on bump stops all the time right now. Secondly upgrade my brakes so they can take whatever punishment I give them.
 
saitrix said:
Also hopefully buying a mk2 front anti roll bar. I already have a thicker one than most mk1's (I have 20mm, mk1s normally have 19mm), the mk2 has 22mm....... Then I can also remove the rear anti roll bar.
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:confused:

Are you trying to increase understeer?

I don't profess to know much about MX5's, but stiffening a cars front ARB and decreasing (or removing) the rear ARB reduces oversteer and increases understeer.
 
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DreXeL said:
:confused:

Are you trying to increase understeer?

I don't profess to know much about MX5's, but stiffening a cars front ARB and decreasing (or removing) the rear ARB reduces oversteer and increases understeer.
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Yes normally it would increase understeer as you have increased the front roll couple for the vehicle. But as I am getting custom springs made up I am picking correct spring rates front and rear to counteract the understeer which the arb's produce. There are a few reasons for doing this:

1) It is always good for traction on a rwd car to remove the rear arb when on rougher road, so say like on most country roads

2) It allows the bounce frequency ratio between the front and rear springs to be further apart on the mx5. Stock the front and rear have near identical bounce frequencies, for best comfort and handling you want it between 10-20% higher frequency at the rear.

So to counteract the lack of rear arb you fit stiffer rear springs than usual, which increases the bounce frequency of the rear with it. So overall you have a car which rolls less, handles better, takes rougher road better and more comfortable.

The reason for the difference of bounce frequency is because the rear axle is always hitting bumps after the front, so by doing this it helps level it out. So yes you were perfectly correct to say that, but because I am doing springs with it I am able to sort it out to give the desired front roll couple I want, ie whether I want more or less understeer.
 
Ahhh Ok, makes sense. AFAIK the Lotus Elise is setup like that from the factory, and doesn't have a rear ARB.
 
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