V5-APS

iTrader: (1)

For all of those people sticking new short blocks into their cars....especially going from 2.0 to 2.5ltr -

How are you breaking in the new blocks - Engine oil, driving regime ??
Also, are you running a 'base map' for 2.5's or sticking with the 2.0ltr map during this period - as i presume it would do the engine no good at this early stage of it's life to put in on a dyno !!

Dyney

I went from 2.0 to 2.5.
I had a running in map put on the ECU (though I was told the std ECU would be fine for running in if I used the std inj's).

I was recommended to run it in on cheap semi-synthetic oil for the first 1000 miles
I disconnected the actuator arm and let the wastegate flap open (so no boost) and set the rev limit to 4000RPM.

After the first 1000 miles I changed to a better semi-synthetic oil and would have raised the rev limit, but didn't get time to re-map the ECU so I ended up doing about 2500miles before getting any boost(1 bar) or revs (limit set at 7k) through the engine

I changed the oil again at 5k and pushed a bit more boost through (1.3 bar) and at 10k I swapped to Motul fully synthetic.
So far so good. doesn't use any oil and no untoward noises

Pavlo

the most important things are:

not to let it idle when completely new.
warm engine up on fast idle (1500-2000rpm)
go out and do about 5 pulls from 2000rpm to 4000 at about 1/2 throttle, each time letting the engine slow you down, then do another 5 or so up to around 5500rpm (yes I know this is above normal running in RPM).

This is a very important step towards bedding the rings in properly, which needs some load, and/or some vacuum to do it well. DOn't let the boost go above 0.5 bar, less if possible. Once it is complete you can go back to the 4000rpm limit etc. While you may question this procedure, manufacturers will do something very similar when the car is produced, but not with only a short engine.

Standard ECU with exising MAF and injectors will be fine.

No need to run in for more than 1500miles in my opinion on the latest engines, as they have much better control over bearing and journal size and shape, and the pistons, rings and bores are better controlled when new. Although personally I would be happy with a 1000miles of varying load, plenty of engine braking and making sure the engine warms up properly before use.

Paul

StickyMicky

who advised this would be fine on the standerd INJ system?
im asuming it was a uk car with 440`s?

StickyMicky

does this apply to imports as well?

ie:
can i have a 2.5 short block fitted to my 97 wrx and run it on low boost etc etc?

Pavlo

A standard car will be fine with a 2.5 even with 380 injectors. It's all down to overall power, if you're not going to be running enough boost to push over 300hp then the injectors will flow enough fuel. And you really shouldn't be pusing 300hp when running the engine in. You are far better off running on standard ECU, MAF and injectors and ensuring the engine runs a good AFR from the first start, than to try and map in some bigger injectors. If you are running on a dyno, and have complete and instant control over the mapping things might be different, but for the average 2.5 rebuild sticking with standard control is the best bet for running in.

Paul

StickyMicky

i rember reading about one of the first 2.5 builds out there who did sumthing simmiler, but i belive his failed, i can not rember the reason for his fail

was he running highish boost?

at the moment i simply do not have the funds there to pay for a 2.5 block, labour and a ecu/remap

but i do need the car for the end of july to drive down south to pick up my G/F`s stuff from her old home, could be a decent enough "running in" trip if its restricted to low boost, and plenty of NF is on tap?

Pavlo

It should run more conservatively on the bigger engine with the same map. The bigger engine will reach the same airflow, and therefor ecu map locations, with less boost. SO say the standard ECU happened to hit about 15degrees of ignition advance with 1 bar, the 2.5 might do that with 0.7 bar, so it should be less inclined to det.

Provided you don't go overboard with the boost it will be fine, keeping the RPM low will limit overall airflow anyway.

Paul

StickyMicky

oooo this works in my favour then

the cost of a 2.5short block was approx the same as a recon 2.0 block last time i checked

i can see a plan forming

DuncanG

Paul, how does the engine braking help break-in? I understand (I think) that load (ie cylinder pressure) helps to push the rings onto the bores for a better seal and quicker break-in, but what does the engine braking do?

Is glazing of the bores caused by too gentle a break-in? If not what causes it?

Pavlo

lots of engine vacuum pulls rings up top of ring groove to help promote sealing, helps stop rings floating about and beds the rings in without combustion upsetting things.

DuncanG

Whats the story on glazing then?

V5-APS

iTrader: (1)

Pavlo,

Does the advice still stand if running in on a PPP map - STi or WRX ??
i.e. Take it gently on the boost ?

Pavlo

If it's a new shortblock then yes. If it's a new car, then the ring bedding in is msot certainly done at the factory and you can just procede as with 4000rpm limit, varying load etc etc

The rings can glaze if there is a combination of not enough load (on the rings) and too much lubrication, so that the surfaces don't actually bed in, leaving the high spots just polished rather than removed. But modern pistons, rings and honing processes need much less running is as they are much closer to being right to start with. Once upon a time, you had to be very careful with too much load too soon on bores as it they had a courser finish that could gall and scrape with abuse.

Paul