posted on February 22, 2011 23:00
Frankenmiata: Dyno Secrets Revealed For The First Time!
by Dave Coleman
One of the best things about LeMons (and there are a lot of great things...) is the complete engineering freedom to do whatever you want (if you can pull it off for $500). This freedom, and full access to MD Automotive's dyno, welders and machine tools, has given us the opportunity to learn a lot about the untested world of crudely-tuned low-boost turbo Miata endurance race engines. It's finally time to share what we've learned. Here's the whole story of the Frankenmiata's, long slow climb from 101 hp to 192 hp as told through 11 dyno charts.
Dyno chart #1: Our base engine was cobbled together from old parts salvaged from 4 different free, blown-up engines. Remarkably, this flailing box of crud put down a respectable-for-a-1.6-Miata 101 hp in naturally-aspirated form.
It seems comically conservative now, but at the time we were so unsure the turbo system would work that we built a non-turbo downpipe, and carried around a stock intake so we could un-turbocharge the car mid-race, if necessary. We also designed the exhaust manifold so we could easily swap manifolds mid-race, assuming the crack-prone stock manifold would shatter when faced with the heat of turbocharging, and made an intercooler bypass pipe to install in the event that some stray auto part pierced our intercooler. None of these precautions ever turned out to be useful.
If you don't remember how we turbocharged this engine for $95, go read about it here.
Dyno Chart #2: The first pull with our newly turbocharged engine was equal parts successful and terrifying. 163 hp wildly exceeded our expectations for our first guess, but it also wildly exceeded what we thought the car could support. Boost first stabilized around 5 psi, down at 3000 rpm, but started creeping as the revs increased. By 7000 rpm, boost was up to a terrifying 7 psi.
Why were we scared by a paltry 7 pounds of boost? First of all because this is endurance racing, and not only do we have to survive 14 hours of constant abuse to finish a race, but we planned to run several races with this engine. Durability was our most important consideration. Most terrifying, though, was our fuel pressure. Our only fuel management was a used Vortech rising-rate fuel pressure regulator that added something in the neighborhood of 10 psi for every pound of boost. Since fuel pressure starts out at 43 psi with no boost, our 100-psi fuel pressure gauge was pegged before we even crossed 6 psi! Not only did we imagine our fuel pump crapping out after a few hours of this kind of abuse, we also had visions of a fiery death when every fuel line in the car ruptured under the strain. (Because of that second bit, we did replace every fuel hose in the car, including the often-forgotten ones back at the tank, with brand new 250-psi GoodYear hose.)
Wednesday, February 23, 2011 1:22 AM
Next time you need orifices for quick and dirty boost control, use nitrous or carburetor jets. I still dip into my tray of nitrous jets once in a while...
You're right too: advanced timing = less EGT = less pre-turbine pressure = lower turbo shaft speed = lower boost.
Wednesday, February 23, 2011 4:14 AM
great read!!! i can follow it but dont ask me to recreate it. true genius lies at motoiq
Wednesday, February 23, 2011 6:11 AM
Sweet holy mother of Kojima, what the fuck! Great write-up Dave.
Wednesday, February 23, 2011 6:41 AM
"Sweet holy mother of Kojima" is the most awesomest phrase I've ever read in a Coleman article, and I've read some awesome things from Coleman.
Wednesday, February 23, 2011 6:57 AM
That is a good line. Now how the eff did you build the frame??? We're still waiting on that one Dave!
Wednesday, February 23, 2011 7:14 AM
What frame are you talking about?
Wednesday, February 23, 2011 9:16 AM
You know what he's after Dave, Project Frankenmiata, the Beginning :) The article where you stitch the front end from one Miata to another. Don't worry 8695Beaters, I'm sure it'll get posted at some point.
Wednesday, February 23, 2011 9:18 AM
aaand this is why my team will never win LeMons. Dyno tuning for us means driving the car around the block and hoping the fuzz doesn't bust us. *sigh*
Wednesday, February 23, 2011 9:21 AM
Yes, Fly'n_Z is right. There's a big COMING SOON in the Frankenmiata geek hub. I remember reading about it somewhere else online, but that was before MotoIQ was taking off. And now I can't find it at all...
Wednesday, February 23, 2011 9:51 AM
Oh that! Yea, I'm getting to it...
Oh, and if you can't find the frankenmiata geek hub, try the search window in the corner, or google. Both work. Meanwhile, we need to add the Frankenmiata to the project cars list.
Wednesday, February 23, 2011 9:55 AM
Great article, lots of good tech and you know how to tell a great story, Dave!
Wednesday, February 23, 2011 11:35 AM
I'm jealous of your brain, Dave.
Also, I'm sure everyone noticed the blue lotus on page 5 but I have to ask; is that a yellow Ultima on page 3?
Wednesday, February 23, 2011 11:47 AM
That's a supercharged K24-powered 1st gen Lotus Exige. Lots of fun stuff at MD...
Wednesday, February 23, 2011 12:41 PM
Project Frankenmiata added to the Project Car dropdown...can't believe we forgot that one!
Wednesday, February 23, 2011 3:22 PM
Fucking sweet ! Keep wrenching Dave. Your stories are hillarious and I learn a ton everytime you post up something.
You guys should REALLY consider about putting out a new mag (like the good 'ol days with SCC). I would totally subscribe. Heck I would tell my mom and ask her to subscribe too !
Wednesday, February 23, 2011 3:47 PM
looks like fenders and a hood are required now. no dual tanks, no homemade refill station...how many other rule changes have you inspired Dave?
glad to see you're back at the smart assery articles. SCC wasn't the same after you said AMF.
Wednesday, February 23, 2011 4:40 PM
was the car in its current state for the Cuba del Norte race? i only got a few glimpses at it.
Wednesday, February 23, 2011 5:36 PM
Yea, the car was in full glory, dyno chart #11, at Cuba del Norte. We realized, as soon as the car started misfiring, that we've been running the same spark plugs for 12 races (we moved them over from the old engine since they're a hard-to-find colder heat range). Other than that, it ran great.
Thursday, February 24, 2011 6:05 AM
@LTDScott - read it again. The real hp bump was just a change that would have been made anyway to clean up that area. The dyno time as much as anything is convenient way to check for overheating, etc. not for power pulls or ECU/ECM custom tuning, etc. Sure it showed the power bump but did not assist Eyesore getting there. Just my 2 Euros...
Thursday, February 24, 2011 6:07 AM
@Dave - 12 races???!!! *slaps forehead reminded of the ngk-r plugs from B13 and their > .05+ gap due to wear* LOL!!!
Thursday, February 24, 2011 7:06 AM
@ Steve - whether shooting for most power or just a safe power level, being able to check and adjust timing, a/f ratio, and boost level to optimum settings by using a dyno sure seems like dyno tuning to me.
But I'm not hating at all, I'm just jealous that they have access to all the cool equipment and goodies that I don't. I'd be using all of that stuff if could too!
Thursday, February 24, 2011 10:22 AM
That lavender vacuum hose is sweet BTW. Did you get it at ricers r us?
Thursday, February 24, 2011 6:15 PM
i thought the turbo looked much less menacing than i imagined it would have been.
here i was thinking that my perception of everything ive seen in internet pictures was way off.
thanks a lot dave.
Thursday, February 24, 2011 7:59 PM
lol. I sold a bunch of that lavender vacuum hose on ebay a few years ago. I bought a 250ft spool at a car show for $20 cause my girlfriend wanted to use it on her car. It was the strangest color hose I'd ever seen. I had about 230ft left over so I ebay'd most of it.
Friday, February 25, 2011 11:00 AM
Frankenmiata reminds me of this:
Saturday, February 26, 2011 12:13 AM
Man I love this kind of build!
Sunday, February 27, 2011 9:01 AM
This is an awesome story...A friend and I are totally sold on putting together our own LeMons car in the future. Thanks for the inspiration!
Wednesday, March 02, 2011 1:57 PM
Dave: Have you ever thought about using E85? It dropped our EGTs while at the same time producing a torque boost. Much higher octane also.
Although, as an endurance car, there is certainly an mpg hit.
Wednesday, March 02, 2011 2:58 PM
Couple of problems with E85:
1: We have no EGT issues now, so that's not a motivator.
2: The air/fuel ratio needs to be wildly different. Enough that we'd need a much more significant re-tune, and that's unlikely to be free.
3: There are only 58 E85 gas stations in all of California.
And #4, you're right, there's an MPG hit, and at this point, that's the most important thing keeping us from collecting another checkered.