Our recent NASA nationals PTC engine build fell a few hp short of the 197whp target we set for it. I wanted to start a new thread about our little chase for 200whp.

After retuning at 4200' elevation MMP (Miller Motorsports park) we got to 191whp on NASA's official NASA MCE owned dynojet last Friday. MCE's dyno usually reads about 3% higher than everyone else's dynojet. My suspicion is that their weather station, being in half closed box just next to the drum will heat soak after all the back to back runs it sees. This was verified when we saw the correction factor climb from 1.19 at am ambient of mid 90's to 1.21 with an ambient of high 80's, same humidity and barometer. The dyno plots showed greater temp at night, thus the temp correction factor climbing after the sun had set. Anyway, everyone was seeing about 5% over local dynojets, and 4-4.5% over the dynojet a few doors down in the garages. I gave that info to NASA and the dyno operator. He added a small fan to the weather station box on Sunday and carefully monitored ambient temps compared to the weather station readings. I think everyone in Sundays races got slightly more accurate and consistent readings as a result.

All this led me to think I couldn't really use Friday's numbers to see where I got to with the build. I want 200whp dammit!

To get the most power per PT points in E and D, we build a blueprinted "zero point" bottom end. Forged rods, .020 over forged pistons, that are cut to give us about .45 more compression ratio that OEM (no points), ARP studs, Supertech double valve springs, stock size plain ss valves (not back cut). That and legal head work gets us about 8-10whp over a crate motor. The rest is intake, header, exhaust, ECU and E85. Crusher got those fabulous sounding 45mm TWM ITB's.

For Crushers motor I had a few more points to play with so we went with +1mm O/S valves, some old Integral cams (.427, 272°IN, .395, 266°EX) in one of our CNC BP4W heads. Same zero point 83.5mm, 10.45:1 bottom end. For what it's worth, Sonny's similar bottom end was torn down for a Whistler test after shattering both TT and PTD lap records. Read 9.9:1. I told the tech guy it must be out of calibration because we knew it to be 10.4:1. Anyway, 10.4:1 is great for pump gas with stock or mild cams but woefully low for an E85 motor. So the plan after returning was to use one of the other bottom ends we have laying around already cut for 85.5mm pistons and a set of custom JE 85.5 12.0:1's we had made for Crusher but never used. For PT, they would add something like 24 points I didn't have to spare. Since Crusher is being retired from NASA club racing, I thought let's do it over and get to 200whp. Dammit.

The new engine will be put into a roadster project that we're building. Windshield frame cut off like an EP but it'll be street legal. We made 191whp on E85 with a BP4W head but I really want the low end torque that a BP6D makes. So we're building an experimental CNC head with +2mm O/S Inconel exhaust valves. Our research to date indicates this is the way to go for big power in a BP head. For cams we'll first try Tomei .426/252°IN, .410,256°EX cams with 33/34mm base circles. Pretty sure those are too short to breath much past 8000rpm but I would like to be proven wrong. On paper at least, they should idle a bunch better than the 272/266° in it now. At the same time, we're having a custom set of BP6D cams made with about the same .425IN/.410EX lift but with something like 270-266° duration. It will be interesting to see what the extra duration does to power and idle quality.

Other stuff we'll add is our damper, 12T trigger wheel and individual cylinder furl trim. It'll probably be 3-4 weeks before we have it together and have it on the dyno. Next stage of development is an easier to tune single throttle manifold. We know have the ability to rapidly draw and prototype a working polymer intake manifold to quickly test different runner lengths on the dyno.
The reason I want to pursue an STB is ease of tuning and reduced intake noise. This motor sounds awesome but is a PITA to tune and probably generates 115db of intake roar. I may be crazy but I still believe it's possible to get to 200whp N/A in a package that will idle well, have crisp low speed throttle response but howl like the dogs of hell at 8000rpm and chirp the tires in 3rd.

 

This is the kind of thread that interests me very much. I think it is possible, and wish you luck.

 

Sounds like you might need to look at headers again?

Or are you planning to do this on an RB?

 

To no surprise I'll follow this carefully.
I'm currently slowly trying to figure out how to tweek the cams to make my overcammed head work somewhat (advancing the exh a bit is the next try, sometime).
My cams have identical grinds (the exhaust should be milder according to "everyone") but the duration at 0.25mm (zero lash/seat duration) only tells part of the story apparently.
My 248 degrees at 0.50" seems more in line with other race related Miata cams.
Found this recent ad that made me wonder what the e-prod heads flow (since the intake lifts quite a lot):
1.8 miata full race Jesse Prather Eprod cams - SCCAForums.com - SCCA Racing Discussions - Sports Car Club of America - Racing Discussion Forums - Market Place - Car Accessories for Sale


The "some old Integral cams (.427, 272°IN, .395, 266°EX)" you used in Crusher, what was the duration at 0.50"?
I'm trying to learn the differences between cam specs between the continents. Yes, the ramp profile matters of course, but it's nicer to compare apples to other apples and not pineapples.

Regarding idle quality, mine idle reasonable well at 950rpm when hot and standing still. Nothing I like to do stop-go driving with though. But my tune is TPS only and non of the enrichment etc have been touched (and no IAC at all besides the right foot).
But just being able to make it run while warming up in the pits is probably not what most would like to call "idle nicely", this after keeping it at 2000rpm for some minute to get some heat.

 

sub'd

 

right now, yes. Do the math on the RB header, it is the correct size already. Not as sexy as a Maxim Works but what, one quarter of the price? There is no point in the exercise if its not easily duplicable by everyone else. If someone wants to send us a Maruha VP and current design MW, I would be happy to do controlled A-B testing against the RB.

 

The header prices vs performance mimic video cards for computers: exponential price for that extra .5% of performance. The RB is a tad pricey, but when the options are $100 Riceland or a $2000 for a Maxim, the RB comes out looking like a steal.

Emilio: When are you going to say "**** it" to cams and make a camless motor? You know you want to.

 

Do N/A exhaust headers work on the same principle as F/I? Hot air in the header will flow faster than cooler air? If so, are you allowed to wrap your header/exhaust?

 

E, are you also planning on testing squaretop vs Honda manifold for this?

 

Coated, as shown in photo

ITB, as shown in photo.

 

In for $20k 10 hour motor.

 

Ahhh, I took "STB" to mean single throttle body manifold.

Photo isn't showing up for me.

 

Pursue != already have

 

Well, both. Right now the 200whp N/A manifold I want does not exist. For purposes of the roadster project, I want ITB's simply because they look cool.
We have a bunch of silly ideas for the roadster. No key, just a push button and IQ3 dash. Removable steering wheel is the key. One piece flip up kevlar/FRP front end. Keisler billet aluminum drop spindles. Windscreen mounted to hood with hidden cowl.

Phase 2 is dinking around with some SLA polymer STB's that can quickly be reconfigured for different runner lengths on the dyno. Once we have some numbers that work, we'll try to figure out a way to serial produce a fixed length version. That manifold would go in the 95R HPDE car we do ride alongs in.

lol, yeah. Trying my best to avoid that. The 1861cc motor we made 191whp with could be duplicated for just under $10k including ECU, exhaust and intake stuff. In a racing scenario, I'd hope for 15-20hrs with average shift point just north of 8k. Drop the average shift point to say 6500rpm and that runs out to 50hrs pretty easily. Drop average shift point down to 5000 like you might see in an aggressively driven street toy and we're in the hundreds of hours.

The new bottom end will cost about the same, just have bigger pistons and more compression to help us get over 200.

 

Props. You always advance the knowledge base and share. Truly appreciated.

 

I am very interested in what will develop without the NASA rules constraining what you can and cannot do. For someone is not focused on an all out race car, I would love to hit the 170whp N/A mark for my GT3 inspired build and get 100 hours out of the engine. What do you think the ticket would be for a 100 hour 170whp engine or is that even a realistic goal?

 

170whp requires more substantial head work or mild cams or lots of compression, pick one.

 

I'm also interested in this.

Personally, I've been just building around a stock engine to see what I can get out of it, given the durability and cheap replacement costs.

I'd like to know what options there are that wouldn't decrease reliability over OEM, or which options (higher redline is the big one, I'd guess, next would be clearances?) decrease mixed usage durability.

Compared to an OEM engine at 7300-7400 (VVT, ECU) redline, would going long rod let you rev higher at an equal rebuild schedule? Balancing?

I'm sure a lot of people here want the big power, but don't want to rebuild more than they have to, as well.

 

We're there now. 1952cc, 10.5:1 on pump gas, ported/polished BP6D head, damper, forged pistons and rods, double valve springs, square top or Honda hybrid, coated crowns, valve heads and chambers. Shift below 7400.

TSE can build that for you.

 

Long rods only make sense at high rpm. You need head flow for that and the BP's don't have it. I'm not a believer in long rods for the BP until it has EP cams and ports to match, shifting at 8800rpm.