Compression ratios

[slowpoke]

Hello ..
Amongst 16bit's very helpful replies to my queries (re: seeking impartial advice) he mentioned that the 10AE had a higher compression ratio(10) than the 1998 NB. I have two Mazda Specification leaflets pertaining to both NB8A ( published in June 1999) and 10AE (published February 1999). The engine specs. are identical for both. The C/R of 9.5 is the same for both also.
Was there a difference in C/R between the 98 NB and the 99 NB ?
Cheers from slowpoke.

[16bit]

i have tried to find confirming information to my previous statement but can not find anything - i would stick with the safer 9.5 when i comes to deciding boost levels for any system. unless you could do a compression test.

[Matty]

There is a lot of conjecture (and no evidence whatsoever) that the 10AE motor was different to the normal NB8A motor. This is the first time I've heard of a higher compression ratio, but balancing, blueprinting, etc have all been thrown around.

[project.r.racing]

dont mazda say they both are 9.5:1? but if looking at turboing, would getting some pistons from a earlier engine or familia/tx3 pistons to bring the comprssion to 9.0:1 or lower?

[Okibi]

As far as I remember the 10AE engine had been blueprinted (to match the paintwork I assume).

I have a brochure at home I'll post here.

[Fatty]

when Woo pulled his 10AE engine down he said it was most definately a balanced engine as the crank and other parts all had balancing marks / machining marks on them from the balancing process. i'm sure he would be able to give a better technical explanation than this, i'm just qouting him (badly) . listenning to him talk about his engine for an hour or so at the garage cafe one night, i soon formed the opinion that this man most definately knows what he's talking about. so his word was good enough to convince me that his 10AE engine was balanced, even tho this point is often open to conjecture as mentioned by matty.

altho maybe i'm mixing up balancing and blueprinting, but i'm pretty sure he said balanced. i don't really understand the difference anyway.

[Woo]

Thanks for a great explaination Fatty, good to hear you were listening to me waffle on.
The finer points to fill in the blanks as was explained to me (and I'm still learning)

The designers make a plan or "Blueprint" of the motor.
Unfortunately, due to machining tolerences etc, the error on the design (although small) grows with every component.
For example:
One motor I built (F2T MX6) put out 137 kW atw with just a few boltons. I then got hold of some Forged pistons that, although weighing the same as the stock pistons, were match weighed to within 1 mg of the blueprint. Those and rings were the only change apart from fluids (it was pretty well maintained and had similar compression).
The power went up to 142 kW atw on the same dyno (Nizpro Bayswater)
That illustrates two things, the importance of blueprinting AND that balancing is important also as it reduces losses.

Back on the 10AE, I would say that the BP is only balanced, not blueprinted.
My machinist explained it this way. The motor would not "need" balancing as heavily as they are IF the motor was blueprinted.
The balancing the 10AE consists of 3 modifications/steps.
Firstly, the crank is very very well balanced. So good in fact the crankshaft guys spun it to 45000 rpm and said it had just a slight murmer. They took the slightest amount out of one of the counterweights and then spun it clean to 50000
They say that if the rest of the motor can handle it I could spin it at 10000 rpm quite safely. Just remember they spin the crank unloaded.
The second part of the balance is the flywheel. All BP's are balanced this way by drilling the perimeter. The 10AE's was perfect and was on the crank at 50000 rpm.
The third part of the standard 10AE balancing is to match the fly to the crank and recheck the balance.

Really though from my experience with BP's (limited as it is) there isn't that much difference as I believe the motor assy plant had really good QC and the parts were close to spec anyway.
I have weighed the 3 standard pistons that came from the old motor and they were good to within 0.5 g .... try getting that close with a Falcodoor

Sorry for digressing
Bazz

Back on topic, I always thought the 10AE was 9.5:1 ..... btw it's now 7:1

[Fuzzlet]

You've pretty much got it there Woo. Blueprinting basically means that those small intolerances are fixed. In my NA, we had the cylinder's rebored (at a significantly larger bore) so that all 4 were in a straight line. Crank then machined and balanced to match. Balancing an engine is definately a good idea, however going to the lengths I did probably wouldnt be needed (looking back I wish I didnt spend the money on the blueprint)

[Matty]

when Woo pulled his 10AE engine down he said it was most definately a balanced engine as the crank and other parts all had balancing marks / machining marks on them from the balancing process. .

James, have a look at the (1.6) crank you bought off me - you'll find balancing drill holes in the counterweights. So the 10AE is no different to this.

[Fatty]

so just to add to the confusion, mazda advertised it as a special feature of the 10AE, even tho they were already doing it to the standard motor anyway

[Woo]

So the 10AE is no different to this.

Sorry Matty, that couldn't be further from the truth.

A stock 1.8 will only spin to 15000 rpm before they it starts really tearing itself apart. The crank guy was very suprised as to how balanced it was compared to the other 1.8's he'd done.

[Fabio]

There is balancing and then there is balancing. You can balance an engine for low revs or for high revs, and you can balance components to within 10grams or 1/4 of a gram, depends on how much time your balancer wants to spend (or how much money you want to spend). Also blue printing is not just making sure that the engine components are within the manufactures spec, (thats what manuf's already do) but to check and then adjust/modify the engine components to a predetermined specification. These specs may or may not be within the original specs, depends on the blueprinters experience and R&D with any particular motor to help it obtain it's optimum performance. Some time you can get lucky, with no real effort put in, and have an engine already at it's optimum, and some times you can have an engine that is with in manuf's specs, but still be a dog of an engine.