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Yet Another Intake Question - Stock Box


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#1 joesci

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Posted 10 July 2018 - 03:00 PM

By a brand new member as well! I must be filling out some bingo cards here.

 

My 1275 MPi is looking to be Stage 1'd. It already has a Fletcher backbox fitted because the stock pipe had effectively rusted into dust, so buying a Stage 1 parts as a 'kit' makes little sense. I figure I just need an LCB Manifold (arguable for MPis I've heard), upgraded intake somehow and some better bits and bobs while I'm at it, like spark plugs, ignition lines and the like.

 

The manifold is easy enough, but I'm sure you all know there seems to be endless debate over the intake, mostly coming down to preference.

 

I've decided against a 57i, for two reasons, I've heard they're no good on injection minis performance wise (is this true?) and also because it seems widely accepted that the stock box with a K&N/PC element inside performs better.

 

So, keeping with the stock box, what are my options? I've read that a stock box with extra holes works the best, but I've also read that this mod shouldn't be done on injection minis. Is there anything I can do with this box, keeping in mind it's an MPI, to squeeze whatever improved performance I can out of it? Would extending/fashioning a longer induction pipe that ends closer to the grill be of any benefit?

 

I've been looking at this

 

https://www.minispor...ction-pipe.html

 

Which quite frankly, looks pretty silly. It looks shorter than the stock pipe so logic tells me would receive warmer air. Why is it so expensive? Is it for the S works badge?



#2 tmsmini

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Posted 10 July 2018 - 04:20 PM

My one opinion on the exhaust manifold is to stick with the cast manifold and get the Maniflow downpipe. I am not sure the LCB has any real performance advantage in everyday driving. I just switched back the cast manifold on two of our cars.

Terry



#3 Wiggy

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Posted 10 July 2018 - 05:35 PM

Anything you do past an exhaust on an MPi is going to gain you pretty much nowt. 'Stage 1' wise, anyway.

 

Rather than buy performance leads, or plugs etc; I'd save my pennys for a better head. Expensive, yes. But that'll make a real difference.



#4 joesci

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Posted 11 July 2018 - 01:48 PM

Anything you do past an exhaust on an MPi is going to gain you pretty much nowt. 'Stage 1' wise, anyway.

 

Rather than buy performance leads, or plugs etc; I'd save my pennys for a better head. Expensive, yes. But that'll make a real difference.

 

Yep, you're right there but unfortunately despite pretty low mile the engine isn't in the best nick, lots of corroded lines, pipes and the like need replacing. My overall intention was to clean up the engine first with these bits then eventually move onto the block itself and see what I can do. The car is a limited edition model so ideally I'd like to keep a lot stock but with it's current condition it needs a bit doing before I move onto serious stuff. Cheers :)



#5 joesci

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Posted 11 July 2018 - 01:53 PM

My one opinion on the exhaust manifold is to stick with the cast manifold and get the Maniflow downpipe. I am not sure the LCB has any real performance advantage in everyday driving. I just switched back the cast manifold on two of our cars.

Terry

 

I've also heard the stock injection downpipes are pretty fine so depending on condition I may end up leaving both the manifold and downpipe as they are. Cheers both.



#6 jamesquintin

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Posted 11 July 2018 - 06:16 PM

I've got the Cooper S kit on my MPI. It came with the cone type K&N and it was very noisy. It was a nice 'roar', but quickly became tiresome. I went back to the standard box with K&N filter, and noticed no differnece in power, although a dyno probably would.

The only mod that I've done to the standard air box is add the square cooper S works intake. Apparently its good for 1bhp... It is significantly wider that the standard round intake (the round intake would fit inside) so its defo getting more airflow.

 

Q



#7 Wazzah

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Posted 09 November 2018 - 04:11 AM

So Ive done the [email protected] thing and an LCB. No discernible difference noticed. The two best things I have done to my SPI is replace all my vacuum pipes and fuel trap which gave me 5 mile a gallon better fuel economy and sorted out a rough idle. The other is fitting a 1.5 to 1 rocker set. Noticeably more mid range punch and pull from 2500 rpm. Top speed still stuck at 140 to 150 kph. I have a worked head on the way and I'll bolt it on and evaluate that before xmas. Gunna stick my neck out and have ordered an SC Plug and Play ECU as well. Had some reasonable results with an old Haltech except for the A/C/ stepper motor interface. Regards Waz



#8 Bobbins

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Posted 09 November 2018 - 10:54 AM

So Ive done the [email protected] thing and an LCB. No discernible difference noticed. The two best things I have done to my SPI is replace all my vacuum pipes and fuel trap which gave me 5 mile a gallon better fuel economy and sorted out a rough idle. The other is fitting a 1.5 to 1 rocker set. Noticeably more mid range punch and pull from 2500 rpm. Top speed still stuck at 140 to 150 kph. I have a worked head on the way and I'll bolt it on and evaluate that before xmas. Gunna stick my neck out and have ordered an SC Plug and Play ECU as well. Had some reasonable results with an old Haltech except for the A/C/ stepper motor interface. Regards Waz

 

Is there nothing else that needs changing when adding high lift rockers, ie. does the ecu self learn to the new fuel requirements for the increased airflow? Like yours mine is a JDM SPi/MPi mongrel.



#9 Bat

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Posted 09 November 2018 - 07:16 PM

Hi,

Best thing for an MPI is to change the final drive!

A 3.1 or 3.2 will give you loads more punch, if you look at the torque figure it should go a lot better than it does.

The MPIs were seriously over geared as Rover didn't want the expense of a 5 speed box...

Cheers  :proud:



#10 Wazzah

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Posted 09 November 2018 - 09:42 PM

Hey Bobbins, I just bolted my rockers on on. The ECU must adjust fuel delivery based on information from the MAP sensor and the O2 sensor. The extra mid range was immediate. I have plans for mine and I'll detail them for you and report on progress. I've ordered a stage 3 head, an SW5 cam  and the SC Plug and Play ECU. I'm also finalizing a 5 speed gearbox just pondering if I will go helical or straight cut. It will be an overdrive box as I drive my mini to work most days. The ratios are yet to be decided but my final drive will remain at 3.2.

A Quaife diff will be fitted when the engine and box are separated. The engine will be bored out to 1310cc, mid 10 to 1 compression ratio and I'll fit a wedged and balanced crank and light rods. Lightened fly wheel at the same time. I'll do all this in stages but the ECU will come first. Head next then I'll swap the gearbox and do the engine internals in Feb. Our club racing scene allows an engine capacity of 1330 so 1310 will allow me another rebore. Ive got adjustable front and back suspension going on the car on Monday. Its got coils with hi/lo's but I'm going back to rubber cones with spax adjustables. I,m 55.5 years old and 2019 will be my first racing season. My plan is to win rookie of the year and the club championship at my first attempt. 

The minister for finance has approved all purchases.



#11 Bobbins

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Posted 09 November 2018 - 09:47 PM

Cheers for that Waz, mine's an air-con model so not so easy to swap the ecu, so trying to work within its' limitations. High lift rockers could be a good start, I'll look into headwork when the engine comes out to sort the gearbox.
Stu.

#12 Wazzah

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Posted 10 November 2018 - 08:11 AM

I've got air con as well. 






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