The chop down turn in is just not being confident. That the car is actually changing direction when you do that means the tires don't already have a lot of slip angle which means you're going in a bit too too slow anyway. Got work up to a slightly higher entry speed so that it's sliding a bit. Some of that is bump steer and 9's catching rough pavement. I'm doing a bit of that in my car too.

Watched a few YT videos on MSR-H CCW from several drivers. On this particular track, not that you asked:

T1. You and everyone else turn in too soon and too slowly. Should be later and more abrupt almost where the tire barrier starts. If you're not nipping over the entry kerb on the right, you're not far enough to the right. It should also be a lift, turn in, straighten slightly then brake in a straighter line then finishing by trail braking into the right just a wee bit.

T2 It's so long that I would hug the inside more and give it a burst of throttle mid turn. Lining up the exit is nice but it's easy to waste a bunch of time camping out for the eternally long 11s to line up the exit.

T7 I would not late apex that either. You go from 120 in the straight, down to 90 or so for the turn then park it at 45mph for the bus stop. No matter what you do, the exit of bust stop is a 48mph 85° turn. Running up the inside of 8 won't change that. If I were racing you, I'd dive up the inside and my lap time would not change.

Entering 7, I would make a diagonal from right left edge to brake later and in a straighter line, finishing by trail braking a bit into the turn. reminds of the old turn before the pits at SMMP.
The very beginning and end of this lap, the fast 90° right just before the pit entrance. http://youtu.be/AorNENnwJNM Same basic idea but applied to your T7.

T8-9. I think I would use more of the kerbs.

T10-17
Nice line through all that.

.02

 

The original NA chassis used for the OGK will become a very low cost E3 car using up a bunch of spares we have laying around the shop.

Talked with Andrew for a long while last night. He would not let me rationalize keeping this a BP4W head. He's right and I know it. Gotta be a VVT head. This BP4W head is such a work of art though. It's just sorta old school to me now without VVT.

The SU/ITE car will be and NB with F/I. The remainder of the plan is TBD.

 

Thanks on all of that. Some of what you recommend is less scary, I like that. I need to work on a few things, one I just added to the list is "how to turn the wheel faster, with grip." I think your advice in 8, while eating up the curb, will buy me a lot of time on that corner alone.

Hopefully now that I have data I'll learn something new.

Thanks for that write-up.

 

I am very tempted to do something similar on the SAAB/Miata, likely minus the VVT head. The more I read the more excited I get.

 

Perhaps I missed it in another thread, but why the RB header? What happened to your super badass argon back filled header? Wasn't it called the Laguna?

 

The RB and Squaretop are most probably not the designed pieces, they might just be what was closest at hand. The Squaretop might be OEM due to rules but the RB header would not be hard to beat at these levels.
Why wait for a new header (sold out, on another car, ...) when you have something that works and it's close to raceday/dyno time?
Even Emilio is human I guess.

Got a message from my cam grinder, identical profile on IN/EX,
10.7mm max lift
1.27 mm 250 °
1.00 mm 256 °
0.30 mm 302 °

It will a bit too extreme with Squaretop+RB, but I don't plan to use them forever
Oh, and the blanks from Mazda did not have enough material on them for the profile without going down to 33mm base circle (my plan was 34mm from the start). The max lift was no problem though. The lifter pockets might not need modification after all.

 

Emilio, Sav,

What percentage of blocks have you sonic checked, have enough meat for the 85.5 pistons?

 

After watching it again, I saw something else. T8 is very off camber. Generally, in off camber turns you want to take a tight line and spend less time turning. The reason is the g load is much lower. So an autocrosss style flick and snap rotate is the ticket there.

Conversely, the apex and exit of 9 has quite a bit of positive camber. Watching G trace form your video and a few others, I see that people aren't hitting the exit of 9 hard and rotating enough there. Average G's should be higher than the other flat turns but I'm not seeing it on the videos with data. When you have a "pocket" like the on at 9, you attack it with a steep fast entry and crank in steering right at the apex to snap the car into a faster yaw rate. At the apex you would want to see a brief plateaur of G maybe .2 higher than the average elsewhere.

None of that is huge but maybe worth .2s combined.

 

Emilio, wunderbar! Just waiting eagerly to see VVT gloria to arrive...

 

I had a VVT head that I considered installing. Looking at my AIM data the revs never dropped below 5k. All of the VVT dynos I have seen show no benefit above 5k. Now I don't know what that extra 1mm of lift from the VVT cams get you but you seem to have that covered.

I would be interested in buying the current BP4W head for my car if you ever want to sell it.

 

Thanks man, great advice, it makes sense.

 

Enquiring minds want to know!

 

Anyone who claims to have this data is a bold-faced liar with absolutely no knowledge of the basic rules of statistical analysis. You would have to sonic check hundreds and hundreds of blocks to determine the percentage of BP blocks that can safely take 85.5 slugs - and even if you were to waste a year or two doing that, you could never safely base any engine building decision on that analysis, because even if 60 or 70% of BPs can safely take 85.5s, that means you have a 3 in 10 chance of grenading a $3000+ bottom end because you weren't smart enough to sonic check YOUR block.

We'll build 85.5mm bottom ends upon request, but the sonic testing that is REQUIRED to run those slugs will cost you extra.

 

I've had these cams for a few years now.

.427 cam lift intake, 272°
.410 cam lift ex, 266°

Clearances are bigger than OEM so actual lift is less of course. That's about the most duration I would run in an engine expected to idle. A VVT head might tolerate another 5-10° since you can dial out some overlap at idle and IVC doesn't really affect idle vacuum.

So these are really midrange cams. Even with IRTB's I would expect peak power to occur around 7700 and roll off to about 8400. Peak torque will still be in the 6100rpm range I think. Our hybrid manifold will still retain the same runner length as OEM so we should have even more area under the torque curve. There are Miata race cams out there over .500 lift and 310° seat duration.

Problem is now that we're already past the power cap for our class so there is no point in looking for more power until the car is retired from PTC in April. That's when the new car will debut. At that point we can resume the path to 200whp. A VVT head would simply have more torque down low and idle better. Neither of which matter for an F/I race motor. For a street motor however, it makes sense to start and high compression N/A project with a BP6D head like our 95R street car.

 

Do you have .050" duration numbers for that cam? Advertised numbers leave us to a lot of guessing. Lift seems pretty stout.

 

Nope, sorry.

 

No problem.

I would like to ask you another technical question. What was involved with the crank scrapers? Does the crank lightening allow you to get the scrapers closer to the crank?

I want to put scrapers on my next motor, but I do not know how well they will work with those damn casting ridges on the crank throws. It seems like a waste without them gone.

Pricey?

 

Actually late IVC does reduce idle vacuum, but with small overlap the idle will be smooth. </nitpick>

 

Neither one of us asked for statistical analysis. We asked for your experience.

I have 6 blocks bored and honed and sitting in my buddy's garage waiting for assembly, and all of them sonic checked fine. I presume that you've build a great deal more 85.5mm engines than the 6 blocks I have had close contact with, and I'm curious if it's common to have a run that long check out at .1" over the stock bore, or if these blocks are as bad as, say VG30DETT blocks, with which you might only have 1 in 5 blocks check out thick enough to punch 2mm over.

 

Actually some data is better than no data (e.g. "out of 5 blocks we sonic tested, 2 had enough meat"), to give some idea of how hard it is to find a block with enough meat. Nobody is suggesting to skip the sonic check.