15 replies to this topic

[sidneyg]

Hi I have a Mini sprite SPI, currentl have a maniflow LCB, de-cat pipe, fletcher exhaust, K&N and all new leads plugs and sensors. Its all running nicely and low mileage (27k genuine). I want to go the next step and up the power a bit. I was thinking about a set of 1.5 roller tip rockers, and wanted to get a worked over head. I wanted some advice and opinions as to what stage head would be the way to go. It wont have to do many miles, its not a daily driver but a weekend fun tool, would like to do the odd event in the future. I Initially thought stage 2, but then wondered if it would be worth going a stage further and having a three. Dont want to have to change the fueling system about too much . Already has wider rubber, uprated suspension and brakes to cope.

What would be your choice?

[datsun100a]

I would start by changing the cam, then move to the head etc. The cam is the weakest point of the spi.

[welshdan]

bolt on parts first. you might find that these give you what you want without removing the engine.

id look at a set of 1.5 roller rockers, and a stage 3 possibly 4 spec head - these vary between companys, some better than others.

if you are after cheap power, try the rockers, and look at getting a used mg metro/1300gt head (both have larger inlet valves, the 1300gt had 11 stud holes,double valve springs and is simular spec to the 1275 cooper s heads.)

i would look at regrinding the valves in (maybe have unleaded seats fitted), and a copy of vizards book and a dremel. give it a light port, smooth the chambers out, then get the head skimmed to the compression ratio that you desire.

this head work would cost probably under 100 quid if done at home (apart from the skimming).

[Cooper-202S]

Assuming in the first instance you want to stick to bolt on mods.

Because you are working within the confines of the existing ecu map, what you are looking to do is optimise what you have. This has a fairly limited scope for cam changes and there are other gains that can be made before you pull the engine apart.

1st step is to make the engine breathe as effiecently as possible, you have already changed the exhaust so personaly I would go for the stage 3 head but with a care to not go ridiculous on the valve sizes, the port work is far more important. 35/36mm inlet 30mm exhausts are about the limit in and unleaded head.

You can also take the opotunity to check the compression ratio, the std SPI runs at 9.75-1 the coopers ran 10.5-1 which is perfectly feasable if you keep the inlet manifold at the right temperature.
Go for flat back type race valves but avoid those with a waisted ( thinned ) stems, there just not necersary in a road car.
The 1.5 rockers will give you better valve lift and does not cause a conflict with the ecu where as a longer duration cam will if you move beyond those listed for Injection.

The inlet manifold will stand some attention to ensure the new head isn't hamstrung.

At this point I would put it on the rolling road and see what you have got going on and check all the senors etc are working.
Your biggest issue will be if the engine leans out badly at the top end. This will cost you the performance your working towards, but more importantly cause an overheating problem that will lead to the head cracking in between the valves and drop a valve seat.

If the engine is persistently running lean then you will need to think about changing the injector or the ECU.
This can be relatively simple if it is a single plug ecu as I believe the 140 and the 170 ecu's are pin for pin compatible
(perhaps someone could confirm this please) If its two plug then i'm sorry i just dont know.
There are injectors that will provide greater fuel capacity but these have to be matched to the ECU and would be a topic all by itself.

The other area you will need to address with a tuned SPI is cooling they have a tendancy towards over heating before you start so tunning will only make it worse.

If you are pulling it to bits then New Cam & put the bottom end on a diet!!!!

Edited by Cooper-202S, 16 November 2009 - 02:35 PM.

[mattwho?]

with bolt on mods what power would you get from a 94 cooper spi? i only have a maniflow bb thats it lol so can we list like 1. 2. 3. what needs doing first then 2nd
i want my cooper more nippy it just feels flat

[datsun100a]

check out the spec of the cam on ml motorsport's forum, it has poorer lift than the old 1.3 metro. This was done to get the emissions down. As has been said above, if you don't mind removing the engine I would defo start there. I've done the bolt on stuff with an spi and it was not a big lot of difference. I used an mg metro head, k'n and lcb, don't know about the 1.5 rockers...

[Cooper-202S]

Order of Preference

Bolt on Mods.
1) New exhaust - Rear
2) K+N Filter element for std box Or similar
3) Med/large bore LCB.depending on head
4) New head stage 2/3 with realy good port work and sensible valve sizes sized for 10.5-1 compression
5) Specialist air filter - removes existing box
6)Open up Inlet manifold to match head
7) Trip to rolling road!!!!!!
8) 1.5 roller rockers
9) COOLING !!!!!!!!!!!
Depending on rolling road results
10) Proffesional advice on fueling upgrades.
Either change 140 ecu for 170 with std injector or 170 with VW injector.
Possibly bore out throttle body. But not normaly necersary uless running the GTA injector and ECU (180)

Engine rebuild Mods

1) New cam shaft & followers.
2) Vernier Duplex Timing kit
3) Wedge Crank shaft
4) Lighten Flywheel
5) Rebore and Expensive Pistons

As to what you will get, then take a look through the rolling road shootouts in Miniworld and you realise that its very variable.

Edited by Cooper-202S, 16 November 2009 - 06:07 PM.

[sidneyg]

thanks guys, some good stuff to think about. In the time I have had the car it runs really nice and cool, never above the 1/4 mark on the guage even when worked really hard in the hilly back lanes at high load low speed. Hopefully this would bode well for the planned mods. This is assuming the guage is correct!!

I am Loath to remove and open the motor at this point. I also would prefer to buy the head ready done. I dont want to have to get too involved in injectors and ECU's so what would you suggest is the way forward, and can anyone name specific brands to use? I just want good useable power. Is stage 3 and 1.5 rockers likely to cause fueling issues? or would I be better stickeing to a more conservative stage2???

Thanks in advance guys, wasnt expecting such a good response

Also Can anyone reccomend anyone in the herefordshire/welsh border area to do the work?

Edited by sidneyg, 16 November 2009 - 06:30 PM.

[welshdan]

theres a rolling road over the valleys, something like highfield/hillfield motors?

they always set my brothers 1380 up, the guy who runs it (tom) is very good. will be sending mine there over next few weeks for power boost adjustment and printout

dont mean to hyjack the thread, but im putting a 1360 in my mpi at the mo. does anyone think i can get anything else from this car spec wise, before messing with the ecu?

73mm bore to 1360cc
standard reshelled crank
centre main strap
home modded head (done according to vizzard) - ported/polished (atched to inlet manifold), standard size back-cut valves reseated, bronze guides, skimmed for cr of around 10.7:1
1.5 Roller tip rockers, double valve springs
new oil pump, new high flow water pump
sw5i cam, followers, piper vernier timing kit
ported inlet manifold, 52mm throttle body (derestricted so it opens to 90 degrees)
K+N induction
maniflow LCB manifold, decat pipe, 1.75inch rc40
fast road clutch plate


gearbox is 1275gt close ratio, hardened diff pin, centre oil pickup, final drive of 3.2:1

am hoping for over 70bhp. can anyone think of any improvements? what power should it be putting out?

thanks

Edited by welshdan, 16 November 2009 - 07:17 PM.

[Cooper-202S]

Sidney g
Any head change needs to be coupled with an upgrade to a LCB.

I would change those, rolling road it and see what you have,
that way you can make an informed choice about the rockers.

Welshdan
Where did the 73mm pistons come from and do the look any good?
Are they the ones with the 11cc dish?
Personaly i would get the crank wedged while your at it, you have spent enough that you will hardly notice the extra.

[welshdan]

Sidney g
Any head change needs to be coupled with an upgrade to a LCB.

I would change those, rolling road it and see what you have,
that way you can make an informed choice about the rockers.

Welshdan
Where did the 73mm pistons come from and do the look any good?
Are they the ones with the 11cc dish?
Personaly i would get the crank wedged while your at it, you have spent enough that you will hardly notice the extra.

lol, from abroad. they are a1 pistons, came with hastings rings, the machinist was well impressed. they have a 6-7 cc dish. the engine is in, just waiting for a mate to change the guides before the head can go back on. if this happens tomorrow hopefully i can get it up and running by tomorrow evening.

[sidneyg]

Sidney g
Any head change needs to be coupled with an upgrade to a LCB.

I would change those, rolling road it and see what you have,
that way you can make an informed choice about the rockers.

Welshdan
Where did the 73mm pistons come from and do the look any good?
Are they the ones with the 11cc dish?
Personaly i would get the crank wedged while your at it, you have spent enough that you will hardly notice the extra.

Maniflow LCB already on, with de cat and aftermarket rear section.

Cheers guys, will consult the bank balance!!

[sidneyg]

Just a little update. Still havnt got round to fitting de-cat pipe thats littering my garage! I have however changed the head!

Bought a reconditioned MG Metro head with the slightly larger inlet valves, new bronze guides, double springs, and a light skim. Have done some sensible mild-ish DIY porting, and fitted it with 1.5 roller tips from Minisport. (I am calling it a stage 2.5 head!)

The difference in drivability and acceleration is very noticeable. The high first gear on the autos takes a bit of pulling from standstill, these mods have totally transformed this and it reall does fly now. No hesitation either. Top speed has remained the same, just under 90. I am going to slim down my huge oversize mudflaps, fit the decat, and get it set up on a rolling road, would be nice if I could coax it past 90. Not a huge concern though to be honest, the power delivery is perfect for a bit of spirited back lane driving.

Will let you know how I get on at the rolling road

One more thing, have been thinking about the ECU swap to metro GTA, but have been told the autos run different ECU's to the manuals and so may not be that straight forward, can anyone confirm or deny this? Also if you fit a GTA ecu are there any issues with immobilisers and the like??

Cheers, Sid

[Cooper-202S]

The auto's ran the mne101160 or 100160 ecu, least the ones i've see do. I dont think there pin for pin compatable with the 180 metro ecu.

It would be a case of going throug the loom drawings and the ecu wiring schematic for both and checking which pin does what.

There is website for reconditioned ecu's that gives the tec's and specs for all the rover ecu's but im damned if i can find it again, but from memory it runs like this.

mne xxx150 Manual upto 65hp
mne xxx160 Auto upto 65hp
mne xxx170 manual upto 80hp
mne xxx180 Manual uptp 108hp.

[sidneyg]

Yep its a 160. So chances are I may be approaching its limit. I have a feeling it is leaning out a bit at the higher revs.

I know this is expensive, but anyone know much about this: http://www.specialis...elated_products they will cover autos according to the advert, may be my only option yet.

I think I read a thread on here a while back that mentioned putting washers in the fuel preasure regulator? cant find it now anyone help?

Edited by sidneyg, 06 December 2009 - 10:16 AM.