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To Dyno or Not To Dyno

PostPosted: Thu Oct 12, 2017 12:01 pm
by MK1_Oz
I have had my engine rebuilt (again :( ) and have run in the new followers and checked the oil pressure. So far so good. Need to run the engine in.

Initially I have set the static timing to 14 and previously measured that the mechanical advance is giving me an additional 24 degrees by 3100 rpm (seems a little early perhaps?). Total advance 38 degrees.

Due to some serious drainage of the piggy bank I am debating whether to get the car on the dyno - is it necessary or not. (New tyres vs dyno....) My thoughts;

Pros
    can run the engine/rings in under controlled conditions
    ensure zero detonation (I assume the dyno would have a knock sensor?)
    set total advance for max torque/power

Cons
    cost
    time


The carbies (45DCOE) are the same as on the previous engine and have not been messed with. This engine has 1/2 a point higher compression and nearly half the squish (down to 0.8 from memory). This one in 1999cc whilst the last was 2046cc. Would have thought the fueling side would still be fine?

Is detonation going to be heard if I have the advance too high or does it tend to silently destroy things? Could it happen at all revs or is it more lightly at lower revs and full throttle?

How much power can be lost by being 1-2 degrees low on advance? Is it worth chasing the optimal setting?

In an ideal world I would just do it but money isn't free!!! Thoughts?

Luxury or necessity????

Re: To Dyno or Not To Dyno

PostPosted: Thu Oct 12, 2017 9:09 pm
by wayovermyhead
In my experience from actually driving my car with a knock sensor that I know was working properly. You won't hear @#$% with all the noise of a race car and helmet on with someone talking in your ear.
The danger zone is through the mid range under load. And to be honest 38 is a lot of timing. Every engine is different but a good race engine with well done chambers shouldn't need anything near that. Out of interest my engine actually made the most power on 30 and anymore just cost power

If you can get it on the dyno. It is worth it!

Re: To Dyno or Not To Dyno

PostPosted: Tue Oct 17, 2017 10:50 am
by Danny M
How did you run the followers in and how long has the engine been running so far?

Re: To Dyno or Not To Dyno

PostPosted: Tue Oct 17, 2017 11:19 am
by MK1_Oz
Followers or 12 minutes @ 2000rpm (some say they need running in some say not).

Total run time 79km + idling in shed. 1-2 hrs. Drove around the hills using 1 gear higher than I would normally to load the engine a little more.

Re: To Dyno or Not To Dyno

PostPosted: Wed Oct 18, 2017 2:27 pm
by Danny M
If you ran the thing at idle for 10-15 mins plus what ever you could have glazed the bores already as that as old wives tale and if the engine made any power there's no way to put enough load on it to bed the rings properly on the street as it'll just wheel spin

Re: To Dyno or Not To Dyno

PostPosted: Thu Oct 19, 2017 8:33 am
by MK1_Oz
OK. That isn't what the engine builder told me though.

Too late which ever way it is......... :(

Has a dyno session next week just to double check the advance and fuelling.

Re: To Dyno or Not To Dyno

PostPosted: Sat Oct 21, 2017 9:48 am
by Danny M
We fire them up just long enough to make sure it runs and then then it's on the dyno with as much load as possible and within your 10 minutes or so the rings have sealed!

Re: To Dyno or Not To Dyno

PostPosted: Sat Oct 21, 2017 12:52 pm
by MK1_Oz
OK. I will try that approach on engine #4!!!!!

Re: To Dyno or Not To Dyno

PostPosted: Sun Oct 22, 2017 2:47 pm
by SportsSedanSteve
When Mike Dale ran in my new engine on the dyno it was really obvious that the rings were bedding in. Engine was breathing quite heavily into the catch can for 5-10 minutes as he held the revs around 4-5000rpm with heaps of resistance on the rollers, the engine sounded like it was really struggling and I thought something was going horribly wrong.

Re: To Dyno or Not To Dyno

PostPosted: Sun Oct 22, 2017 8:27 pm
by jpayne
I have nothing to add other than say I hate being there during Dyno sessions. Listening to the poor engine from the unnatural position of in front of it as the operator does what they do...just don't like it!

JP