Padstar
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| posted on 15/7/12 at 11:00 AM |
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MX5 1.6 vs 1.8
I currently have the older 1.6 model as a donor for the running gear. I would like the best performance possible from the build so will the 1.6 cut
the mustard or should I change now before I start?
I have heard that the diff from the 1.6 is inferior to the latter model. Is this true?
Final thing is are the mounting points the same for each MX5 engine and transition the same (ie will I be able to pull the older one out after
registration and change for the newer at a later date if I wanted to
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chillis
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| posted on 15/7/12 at 12:28 PM |
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To answer your last question first: The front subframe that the engine bolts to, is the same as is the gearbox. Flyin' Miata do a conversion kit
so you can keep your existing engine management. This includes engine mounting brackets, throttle body adapter, egr blank, coil pack bracket and a few
other odds and ends.
If I were building a seven style car I'd stick with the 1.6L, it makes all its power at the top end and feels much more like a sports car
engine.
I've done nearly 200000 miles in my '92 mx5 1.6L and had no trouble with the (vlsd) diff, which contrary to what everyone claims, is still
working, and has a better ratio for a sports car anyway.
You could easily build from a 1.6L base if thats what you have and fit a 1.8L motor later on if you felt the need.
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bigdrew
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| posted on 15/7/12 at 12:34 PM |
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If it is a late UK 1.6 (after 1994) it will only be the 88HP engine, which you don't want. If its a Jap import (Eunos) it will be 118HP
regardless of its age.
The 1.8 were more like 130HP I think.
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skov
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| posted on 15/7/12 at 01:27 PM |
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I'd stick with the 1.6 (I have!).
It's 'revvier', and the 1.8 running gear supposedly carries a ~40kg weight penalty which will negate much of the additional
power.
If I find I want more power in the future I'll either turbo it, or stick a Mk2.5 1.8 in there, which bolts straight to the gearbox and is around
150bhp in standard trim.
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coozer
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| posted on 15/7/12 at 01:36 PM |
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Stick a V8 in it.
1972 V8 Jago
1980 Z750
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Not Anumber
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| posted on 15/7/12 at 02:33 PM |
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The 1.6 will provide plenty of power especially if its the 115/118 bhp version. Use what you have and if you feel you need more power at any stage in
the future you can go for the turbo conversion.
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Chippy
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| posted on 15/7/12 at 03:10 PM |
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quote:
Originally posted by Not Anumber
The 1.6 will provide plenty of power especially if its the 115/118 bhp version. Use what you have and if you feel you need more power at any stage in
the future you can go for the turbo conversion.
Or do a Claire and stick a V6 in it.  Cheers Ray
To make a car go faster, just add lightness. Colin Chapman - OR - fit a bigger engine. Chippy
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indykid
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| posted on 15/7/12 at 03:29 PM |
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The 1.8 has bigger brakes, bigger clutch and the option of a Torsen diff. All can be retrofitted to a 1.6 (you need the shorter 1.8 prop (so weigh
this up before you get a prop made) and halfshafts to fit the diff) so it's not the end of the world if you don't get them on your
donor.
The 1.6 is the better engine though imho. I've had both in mx5s and the 1.6 felt just as quick as the 1.8 I have now. It absolutely loves to be
revved.
The 1.6 diff has been known to strip teeth off the ring gear and crack bearing caps, even with stock power, but you shouldn't have any problems
with the weight of a locost, or if you drive with even a shred of mechanical sympathy. It's only available in open and VLSD flavours though.
The 1.6 diffs are 4.3:1, the 1.8 diffs are typically 4.1:1 (though also come in 4.3, 3.9 and 3.6 ratios from the RS Ltd and 6 speed box versions)
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bigdrew
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| posted on 15/7/12 at 04:47 PM |
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Don't expect the VLSD to work anymore unless you are very lucky, most are just open. Mine certainly is!
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Padstar
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| posted on 15/7/12 at 05:50 PM |
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My donor is a 98 uk spec so will it only be 90bhp? My first saxo 13 years ago had more horses?
So I am getting the feel from most of you guys that the 1.6 is a good option? Should I be looking to match with a later dif? I should have the dif
striped out and cleaned up in the next few weeks so will see what condition it is in before I make any rash divisions
It's good that the later 1.8 bolts straight into the earlier gearbox.
Using the engine and transition from the donor should also get me an age related plate of an R. I want to try and avoid a Q if possible ( for the sole
reason that I can then get a private plate if I wanted to)
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chillis
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| posted on 15/7/12 at 07:20 PM |
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quote:
Originally posted by bigdrew
If it is a late UK 1.6 (after 1994) it will only be the 88HP engine, which you don't want. If its a Jap import (Eunos) it will be 118HP
regardless of its age.
The 1.8 were more like 130HP I think.
I believe the post '94 Eunos import is still 115HP the 88HP engine was mainly for the U/S market.
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chillis
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| posted on 15/7/12 at 07:24 PM |
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quote:
Originally posted by Padstar
My donor is a 98 uk spec so will it only be 90bhp? My first saxo 13 years ago had more horses?
So I am getting the feel from most of you guys that the 1.6 is a good option? Should I be looking to match with a later dif? I should have the dif
striped out and cleaned up in the next few weeks so will see what condition it is in before I make any rash divisions
It's good that the later 1.8 bolts straight into the earlier gearbox.
Using the engine and transition from the donor should also get me an age related plate of an R. I want to try and avoid a Q if possible ( for the sole
reason that I can then get a private plate if I wanted to)
A '98 1.6L should have the later 7" diff like the 1.8 but with a better ratio. Only pre '94 1.6L had the small diff. So you should
be good to go and fit the 1.8L engine later on.
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chillis
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| posted on 15/7/12 at 07:27 PM |
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quote:
Originally posted by bigdrew
Don't expect the VLSD to work anymore unless you are very lucky, most are just open. Mine certainly is!
My V spec VLSD has done almost 200000 miles nearly 320000Kilo's and it still works! But the VLSD doesn't work like a plate locker which is
generally why most people don't think they work/have stopped working.
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indykid
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| posted on 15/7/12 at 07:36 PM |
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Chillis, you're feeding in a lot of misinformation there.
The mk2 1.6 got the 7" diff and bigger brakes.
If it's a UK car on an R plate though, it's a mk1, so is 88bhp and has little discs and the weak diff. There were no JDM mk1 1.6s made
post '93, only 1.8s. The UK market got the derated 1.6 to make a gap between the 115bhp original car and the new 130bhp 1.8.
I'd be inclined to find a different donor as you have the least desirable of all the bits, though what you have will give you a running car.
Being an R plate though, it'll need a cat. I'd try find an earlier one.
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bigdrew
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| posted on 15/7/12 at 09:14 PM |
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quote:
Originally posted by indykid
Chillis, you're feeding in a lot of misinformation there.
The mk2 1.6 got the 7" diff and bigger brakes.
If it's a UK car on an R plate though, it's a mk1, so is 88bhp and has little discs and the weak diff. There were no JDM mk1 1.6s made
post '93, only 1.8s. The UK market got the derated 1.6 to make a gap between the 115bhp original car and the new 130bhp 1.8.
I'd be inclined to find a different donor as you have the least desirable of all the bits, though what you have will give you a running car.
Being an R plate though, it'll need a cat. I'd try find an earlier one.
They are so cheap and easy to get hold of I think a new donor would be your best bet...
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Padstar
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| posted on 16/7/12 at 05:50 AM |
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Thanksfor all the help guys. Can u suggest what model I should go for so that I get the correct donor this time round..
My only issue is that I don't have the space to break a donor car down so need to buy it as already fully broken or at least the running gear
only that I can finish breaking in the garage.
I plan to use new steering, upright, hub and break gear so I require limited parts from a donor vehicle
Just to be sure we are all confirmed that no mater what model I go for the mounting points are the same (this will allow me to crack on with the
chassis)
[Edited on 16/7/12 by Padstar]
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indykid
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| posted on 16/7/12 at 11:02 PM |
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quote:
Originally posted by Padstar
Just to be sure we are all confirmed that no mater what model I go for the mounting points are the same (this will allow me to crack on with the
chassis)
Yep, crack on 
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