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My SE's rebuild will be finished shortly including a forged bottom end, stronger valve springs, uprated clutch, coolant reroute and bigger rad, bigger injectors and a stand alone ECU.

The builder is advising me against using it as my DD because, he says, doing so will cause undue wear.

The drive to work is less than 5 minutes and is low speed and requires very little throttle. Yes, I can sometimes walk or cycle to work by the way, but I still want to try to avoid owning a second car if possible.

So can I safely use the car for these short trips without significantly accelerating the wear on the motor?

I don't like the idea of running a motor with no load but is there maybe a middle ground involving warming the motor up before setting off?

Short 5 minute trips are the worst thing you can do to an engine. It never gets hot, oils always way too thick, even if it was standard it's not good. Walk or ride, drive the car in the rain if it's bad.

Sent from my GT-I9100 using Tapatalk

Just warm it up

Its not the only forged engine in australia... Pedantic advice really.

sailaholic wrote:Short 5 minute trips are the worst thing you can do to an engine. It never gets hot, oils always way too thick, even if it was standard it's not good. Walk or ride, drive the car in the rain if it's bad. Sent from my GT-I9100 using Tapatalk

Thanks for the advice. I'd better get the cycle repaired. Hopefully it'll be quicker and cost less $$$$ than the SE!

However, I promise you there are worse things I can do to an engine.

By the way, the difference between having a company car and accepting a car allowance instead amounts to over $8,000 a year after tax, which is why I don't take the company car, especially as I'd mainly use it for only 2 x 5 minute drives per day.

NitroDann wrote:Just warm it up

Its not the only forged engine in australia... Pedantic advice really.

Thanks for the advice Dann. In what way would warming it up be better than driving it very gently straight away?

Forces on reciprocating parts is squared with engine rpm.

So 2000rpm is 4 times the force on the rod and main bearings, not double. 3000rpm is 9 times the force.

So get the oil and parts warmed and to the correct tolerances before going 3200rpm cruising gently down the road at 10 times the forces than idling.

Dann

A cousin of mine was a race engine builder: operating theatre cleanliness on alfas, fezzas. lambos, that sort of stuff.

During speeches at his wedding his brother turned to the bride and asked "Now Dianne, you wake up in the middle of the night and the bed is soaked. Your waters have broken, contractions are coming every minute, you're confused and it's very painful. Stephen is up at Bathurst at a meeting. You manage to grab your bag and make it out to the garage. What do you do next?"

Without the slightest hesitation she said "Open the garage door, start the car, let it warm up for 4 minutes and then drive off."

Who says your drive to work is less than 5 minutes?

Apu wrote:Who says your drive to work is less than 5 minutes?

4 minutes in a 1979 Mazda 626 auto. I'll go 25% slower in the SE.

NitroDann wrote:Forces on reciprocating parts is squared with engine rpm. So 2000rpm is 4 times the force on the rod and main bearings, not double. 3000rpm is 9 times the force.

So get the oil and parts warmed and to the correct tolerances before going 3200rpm cruising gently down the road at 10 times the forces than idling.

Dann

Thanks Dann. That's answered one of the Mysteries of Life for me and pretty much helped me decide not to buy an extra car. Any other thoughts to minimise the downsides of using the SE as a DD?

Get a new 3 drive car and leave the mx5 at home. I have a similar engine spec and can't imagine using it as a daily

chops wrote:Get a new 3 drive car and leave the mx5 at home. I have a similar engine spec and can't imagine using it as a daily

New M3 is an excellent car but if I had one as a company car it would cost me $8k per year in tax and lost car allowance. I have better things to spend $8k on, especially this year with a family wedding to attend in the UK.

chops wrote: I have a similar engine spec and can't imagine using it as a daily

Why? Its extraordinarily tame. Might as well be stock.

Dann

It is a nice idea to just warm it up every day but I think you would get sick of that real quick or not do it and end up damaging it

You wont damage it any more than a stock engine, its just that if you wear it out in 100k its more expensive to replace.

As for warming it for 3 minutes... Come on. A day has one thousand three hundred and thirty seven more minutes left over after warming it up.

Dann