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Camshaft In My Jdm Spi( With Mpi Block)


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#16 Bobbins

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Posted 14 December 2018 - 04:12 PM

Coincidentally I've been thinking about engine mods same as hungdynasty and also need details about the cam that's used in the JDM spec Minis. I'm under the impression that the ecu in my '98 JDM Cooper is specific to the model with it being distributorless SPi with air-con, but I don't have the knowledge to work out what that means relating to the cam - my assumption is that the JDM will run wasted-spark therefore won't need a cam-phase sensor?

 

I'm also led to believe that the ecu will be self learning and will be fine coping up to about 85bhp?

 

The only JDM specific upgrade kit I can find is the Minisport Cooper kit specifically designed for the Japanese cars and there's a lot of stuff in the kit that's not needed, plus it's priced at a healthy premium. I'd prefer if it's possible to have the headed ported and fit high lift roller rockers and an appropriate cam, the cam's the bit that it's hard to work out the required specification!



#17 Wiggy

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Posted 14 December 2018 - 06:40 PM

The MPi is wasted spark with a cam sensor.

As far as I'm aware, if you have a cam sensor, you must use an MPi cam. (Down the back of the engine on the near side.) Because they have the sensor pickup. SPi cams are the same as any other cam, just specifically profiled to suit the ECU and emission requirements.

I believe.

#18 Retroman

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Posted 14 December 2018 - 07:48 PM


 

I want to do some upgrade on my engine and as I can see many aftermarket upgraded camshafts are specified not for mpi engine, I just want to make sure what to use because of my mpi block.

 

Ok So you have an MPi block but its running SPi injection

 

Also no dizzy to drive, no cam sensor to use or no mechanical fuel pump lobe

 

The cam in it is unknown and could be anyting from anywhere, but you are want to upgrade it, which is fair enough.

 

The only worry you have is the emmissions and the ECU / fueling

 

You could use a MDM274 no issues with emmissions and the standard ECU can cope

 

http://www.retromini...roducts_id=1138



#19 Retroman

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Posted 14 December 2018 - 07:54 PM

Forgot to say 10% off for TMF membership too



#20 nicklouse

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Posted 14 December 2018 - 07:55 PM

 

 

I want to do some upgrade on my engine and as I can see many aftermarket upgraded camshafts are specified not for mpi engine, I just want to make sure what to use because of my mpi block.

 

Ok So you have an MPi block but its running SPi injection

 

 

Nope, some one else does. ;)



#21 Wazzah

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Posted 14 December 2018 - 11:02 PM

It is my understanding that the JDM SPI cams are identical to the MPI motors. These cams are very good as they are. They perform as good as the old Cooper S cams with a more aggressive exhaust profile. These cams keep the exhaust open a bit longer and close off quite dramatically. Both SPI's of the jap variety and MPI's respond well to 1.5-1 rocker ratio changes. Having said all that I couldn't resist buying an SW5. Probably whack that in after xmas.



#22 Wazzah

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Posted 14 December 2018 - 11:11 PM

And the crank angle sensor works of the flywheel in both JDM SPI's and MPI's. The flywheels are notched and have 4 notches missing. 2 missing notches are 180 degrees apart and signify the two top dead centres. The other 2 notches are 2 notches past top dead centre and I believe they fire the injectors quickly after the first squirt in order to rectify the siamese port robbing effects of the 5 port head and the mini's firing order.



#23 Bobbins

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Posted 14 December 2018 - 11:26 PM

So are you suggesting there's no advantage in using a 274 (scatter pattern) cam?

#24 nicklouse

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Posted 14 December 2018 - 11:31 PM

So are you suggesting there's no advantage in using a 274 (scatter pattern) cam?

to answer that i have to ask a question what is the advantage of a scatter pattern cam? if you know the answer then you will know if it may help or not.



#25 Bobbins

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Posted 15 December 2018 - 08:30 AM

So are you suggesting there's no advantage in using a 274 (scatter pattern) cam?

to answer that i have to ask a question what is the advantage of a scatter pattern cam? if you know the answer then you will know if it may help or not.

Experience from people who've used one would help, I can only go by the information provided with the cams. My more recent engine rebuild experience is with high power K-Series engines, it's 35 years since I did an A-Series rebuild and IIRC the preferred road/rally cam then was a 510! I guess things have probably moved on a little though, I'd not heard of a scatter pattern until I started researching choices for the A-Series.

#26 mini13

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Posted 15 December 2018 - 09:15 AM

Essentially the idea of a scatter cam is ti treat the engine as individual cylinders and time them accordingly to make the most from the a series head quirks, it's really more effective on more racy cams,

#27 Retroman

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Posted 15 December 2018 - 08:49 PM

The MDM274 we sell is not the scatter pattern type

 

I think a longer duration / higher lift cam and a higher state of engine tune is needed to benift from a scatter type profile

 

Pretty sure David Vizard realised this too and did not produce a scattered cam less than a 286

 

  The whole concept of scattering the timing is to reduce the charge robbing between cylinders sharing a common inlet port...as they draw air one directly after the other.

On a scatter ground cam all the lobes are the same but 1 & 4 and 2 & 3 as pairs are timed 2 1/2 to 3 degrees differently.

 

The theory in my head is that charge robbing is worse on longer period cams, so they benifit more from the scatter grinds,

and should result in an increase of 3 - 6% more grunt.

 

That said we do plan to try a one off grind....

A short duration / high lift / longer exhaust / scatter pattern / mega tight LSA  with a near standard head / small valve, small bore, single carb as a 'developement'

....words foot mouth

Who knows with the gas speeds involved, it might just eek out a few more Lb of torque






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