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PostPosted: Thu Dec 28, 2017 5:50 am 
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Jesse,

I took a couple minutes and tried some combinations and figured out the curtain area as it relates to cylinder volume. You’ll see how the valve lift specs of the Miata even it out. Some look more competitive than others (and no, it’s not the Miata). :wink:

I also took some Level 1 combinations and back calculated to figure out how much valve lift they need to equal a certain ratio (as above). Some combinations are a lot more doeable than others (the MG 1275 looks a lot better than you’d think). Of course, a Level 1 engine has a lot more allowances. I’ll post more when I get some time as it’s an interesting study.

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PostPosted: Thu Dec 28, 2017 7:38 am 
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You have to remember and Jesse alluded to it, its not always motor that gets you to the front of the field. Look at some of the races the last couple of years in EP. You have a FWD racing a RWD and they are both fairly evenly matched (until the FWD burns up the front tires, HAHA).

Being a chassis and drivetrain nerd, I think there is tons of development yet to be seen in a full tilt level 2 type build. One thing that will hurt the Saturn and many other FWD mac strut vehicles is the limitations placed on the upright modifications. Yes you can change the shocks, but that is only half the picture. The mac strut gets hammered in the rules and that will really limit how much you can optimize the front suspension. Add to that the beam axle in the back and you will have a tough time getting the suspension to work on the car. The development of a new car involves more than just motor and the Saturn Chassis is pretty hampered by the rules.

You might find an advantage by keeping the RPM low and building some custom gearing in the transmission to keep the engine in the meat of the torque curve at all times. Basically treat it like a diesel, but I suspect with the 5spd trans you won't have a bunch of gear choice options though.

https://en.wikipedia.org/wiki/Saturn_MP_transmission

The stock ratios look REALLY wide, but the MP3 transmissions have better gearing. You might could figure out how to gear the car to use 2,3, and 4, assuming there are any options for final drives. What kind of differential is available? I would probably look at tossing the Saturn trans and adapt something that will have more usable options and probably better durability.

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PostPosted: Thu Dec 28, 2017 7:18 pm 
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Thank you all for the input and advice. Just out of curiosity, what order of magnitude is a top FP/EP limited prep build for a Miata cost? Just want to understand the differential between a developed engine solution and an R& project...

The suspension is coming along nicely - I really am enjoying the engineering challenge behind it. That said, it is 100% a custom solution - lots of trial and error and learning the impact on my car (versus others) and how to adjust from it. There is still a loose nut behind the wheel, but it is slowing getting tightened as well.

As for the transmission, well, that is in the same boat as the engine. 5th gear SUCKS and really sucked the fun out of going down the straight at Indy. I do have a few easier solutions here, but no point in solving this problem before many of the others are sorted. The differential is a Torsen limited slip (Thank you Saturn ICY World challenge team!) and has been proven pretty robust.

I'm stuck between the old saying "the cheapest racecar is the one you already own" and the fact that I will get very little of my investment back in the current car vs buying something else. Plus, I'd have to change my screen name and email address... :D

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Bill H
92 Saturn SL2 - SCCA F-Production


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PostPosted: Thu Dec 28, 2017 9:11 pm 
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planet6racing wrote:
"the cheapest racecar is the one you already own" :D
That is only true if you don't plan on changing anything and race it as it is. If you race it as is you will never be able to evaluate your driving ability as there will always be something that the car needs to make you as fast as the other guys, and it will be the excuse that you tell yourself for why you aren't going faster. That is the way this game works - it isn't until you have everything that can be had before you realize that you might not be capable of doing what the guys up front can do.

Please don't take this the wrong way, and I hate to pop your balloon, but you really need to decide where you want to be in as many years down the road as you dare to look. Are you soldiering around mid-pack in a car of your own design that you feel proud of because you did it all, or do you desire to run with the big dogs? If you think you can engineer a suspension and engine package that no one else has AND run up front you will spend an order of magnitude more than what it would cost to buy a competitive car. And, after spending that amount of time and effort, you may not be able to run at the front with any amount of money because you may just have the wrong horse. When you go to the comp board asking for adjustments that favor your car you will most likely be told that you do not have a good enough program for them to evaluate the performance potential of your one-off car and program.

My car is a good example. I can document every part on the car, what it cost, what it is worth in terms of street value, and what the whole package with everything would sell for. With no labor included it would cost way more than double to duplicate my car from scratch. And that is a car model that has been raced for over fifty years by hundreds of people with probably 10 professional shops selling the modifications, each trying to be better than the other guy. The Miatas have been around for a while and enjoy a similar situation in terms of level of development. You are on your own.

If you eventually want to run up front, my advice to you would be to try to understand whether you can drive. Don't waste any money on your current car until you understand whether you can get the job done. You can start that process in your current car but may need to have something similar to the other guys in order to be sure. If you can drive, now you can properly evaluate whether the car is holding you back or not. Without that information it will always be assumed that it is the car.

If you have no desire to run up front, then have at it. It will be a fun project but it just might not yield any worthwhile results, and you will spend a lot of money over time.

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Last edited by Ron Bartell on Fri Dec 29, 2017 7:09 am, edited 1 time in total.

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PostPosted: Fri Dec 29, 2017 5:28 am 
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One more comment re simulation -

You will need a very good software package and an extremely well researched model to give the best results, and as Jesse points out, even then you won't know exactly 'til you can tweak on the dyno.

BUT

A reasonably good software package and a reasonably good model should give you some really good guidance as to the approximate capability of the engine and a good idea as to the bottlenecks. It won't tell you for sure that cam x is the best setup, but could give you a pretty good idea what sort of power the engine might make. Much cheaper than building and maybe more valid than rules of thumb based on throttle plate diameter.

Or a more empirical approach might be to simply get a shop to flow an intake port with manifold and TB attached - running that number by an experienced builder will probably give a good estimate of power potential.

Also - a private talk with some experienced racers will probably yield some solid crank or wheel horsepower numbers (at least ballpark) from front running cars.


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PostPosted: Fri Dec 29, 2017 7:08 am 
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First: In reviewing this thread, I realized I have forgotten something:

Mr. Dewhurst - I apologize for not fully reading your post and assuming you were suggesting cheating. You were not - I simply skimmed the first part and jumped straight to your suggestion of using an alternate part for dyno testing. I apologize.

As for what I want to be when I grow up (something I still don't have an answer to in real life)...

Starting this year, I was happy to slowly develop the car and be back to mid pack, rationalizing that the amount of money required to get up front was too much and that I was not willing to spend it. Then, a couple of things happened. One, I (loosely) kept track of how much I spent this year and how far that advanced development. Comparing this to some of the classifieds posted through the year, I started to ask myself what I was doing. The second thing is my wife (best wife ever!) asked why I was happy running where I was an not moving toward the front. I gave a lame answer (do we want to spend that much money?) but that has been sticking with me ever since.

Oh, and then there was the Runoffs. Just trying to figure out how I could be in the top 33 so I could be on the pylon. That was a bit depressing as well.

I know I need to make a decision on where to go. I just want to insure it is an informed decision. The throttle body size examination was just the start of answering the question "Can we really make this car race at the front given a reasonable budget (recognizing it is fully R&D)?"

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Bill H
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PostPosted: Fri Dec 29, 2017 7:17 am 
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Jesse,

Here is a little sample of the spreadsheet I put together:
Image

Everything should be pretty self explanatory. The 'theoretical' columns, I used 12% as a target VCA/D as it seemed in line with other competitive models. I then back calculated to produce a valve lift target. As you can see, the only one that can meet that number and exceed it is the BMC A-Series engine and Spitfire. I'm sure others could creep up to their targets with a ton of money put into the valvetrain (CEA, custom rocker systems, tool steel cam cores, Spintron work, lots of custom parts... ). Which it should - it's a small engine and it needs to be making more power/L than the bigger engines. It also loses out on intake harmonic tuning due to the siamese ports, so it's not as clear cut as an 8-port head like a Spitfire, which has a much better head. Of course, this is only one variable.

Not sure why you're bothered by the SIRs. The engine doesn't matter where it's choked at - the SIR, or the valves, carburetor chokes, or ports, what's happening inside the cylinder is still the same. You reach sonic choke somewhere in the system and pumping losses begin to outrace the the mass of air that can get through wherever it's choking. You build a LP engine the same way - hold on to the power as long as you can, even as mass flow is choked.

All,

As far as 1D simulation goes, again it's all about knowing your limits - Garbage In, Garbage Out. People build a model and then just start changing things and act shocked when it doesn't match the real world.

Once you have a model in place, you should only change the intake tuning length, lash, and exhaust tubing diameter and length. Any other change will require a re-measurement. Even a change in bore size will effect valve shrouding and the flow curve - that should be rerecorded on a flow bench. Any flow related change must be tested on a flowbench to be put into the model.

Camshafts are the trickiest part as you'll need real information (from a Cam Dr. or a S96 file from your cam grinder) or a very good camshaft model.

To build camshaft models, a very good, cheap camshaft design program is this one: http://www.mjpsoft.dk/cam_instructions.html You can design a flat tappet (or OHC bucket) or a roller profile (and actually use it). It uses C-Splines, so it's not the most powerful cam design program. The more expensive programs use higher level mathematics for smoothing and other curve development math, which allows one to fit more lift area while still maintaining your velocity, acceleration, and jerk constraints. They will also allow you the ability to work backwards through the valve lift curve to produce a lobe profile. The latter is a MUST for a OHC rocker type engine. A real cam design master will likely be able to find you more area under the curve (and be easier on the valvetrain) then you'll likely come up with, but this is sufficient for modeling.

With a bucket or a flat tappet, the velocity is fixed by the diameter and how close you want to run to the edge of the lifter. When NASCAR ran the .875" flat tappets, they used no chamfer and ran the lobe all the way to the edge of the lifter to maximize their velocity. Of course this requires very accurate lifter bores in relation to the cam lobes and some very tight machining tolerances.

If you guys have Cam Dr. data and want to look at what you have, you can use this equation:

Edge Distance = -1((Velocity*57.3)-(Tappet Diameter/2))

Velocity is in inches / degree.

This will allow you to see what safety factor your cam designer is using. Pushrod engines, designers typically use .018-.020" for off the shelf stuff with a typical chamfer. OHC with stiffer valvetrain systems might be as tight as .009" for off the shelf designs. With work, you can tighten those up and gain more velocity which equals more lift area.

Use this equation to plug and play and see how much velocity you could have:

Velocity = ((Lifter Diameter/2)-Edge Distance)/57.3

This will impact how much lift area you can have (even with valve lift limits).

Acceleration is the tricky one, but this should get you started for engine simulation work.

Enough for now...

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PostPosted: Fri Dec 29, 2017 8:17 am 
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One easy way to fix a crappy 5th gear is not to use it. Not sure what FD ratios are available but you could put a taller one in. I did this on a friends ITS Intgera and it really helped. Fifth gear is well over driven and 4th is basically 1:1.

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PostPosted: Fri Dec 29, 2017 11:35 am 
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planet6racing wrote:
First: In reviewing this thread, I realized I have forgotten something:

Mr. Dewhurst - I apologize for not fully reading your post and assuming you were suggesting cheating. You were not - I simply skimmed the first part and jumped straight to your suggestion of using an alternate part for dyno testing. I apologize.

As for what I want to be when I grow up (something I still don't have an answer to in real life)...

Starting this year, I was happy to slowly develop the car and be back to mid pack, rationalizing that the amount of money required to get up front was too much and that I was not willing to spend it. Then, a couple of things happened. One, I (loosely) kept track of how much I spent this year and how far that advanced development. Comparing this to some of the classifieds posted through the year, I started to ask myself what I was doing. The second thing is my wife (best wife ever!) asked why I was happy running where I was an not moving toward the front. I gave a lame answer (do we want to spend that much money?) but that has been sticking with me ever since.

Oh, and then there was the Runoffs. Just trying to figure out how I could be in the top 33 so I could be on the pylon. That was a bit depressing as well.

I know I need to make a decision on where to go. I just want to insure it is an informed decision. The throttle body size examination was just the start of answering the question "Can we really make this car race at the front given a reasonable budget (recognizing it is fully R&D)?"


Bill, let me pipe in an address some of your comments and tell a little story. Nine years ago I found myself without a car to drive, I had an old GT5 car that I was going to build into a GTL Car but the build process just seemed too daunting at the time. I came across a deal from an old time racer that was getting out of the sport. He had a half built FP Miata that he had been trying to sell for a year with no luck. Finally out of desperation he posted an comment on our local forum that said if someone would just buy his tow rig he'd throw in the Miata and trailer. He didn't even say what the tow rig was...poorly written ad! Turns out it was a three year old Cadillac Escalade ESV with tow package. His asking price for the Caddy was $3k back of book and I figured how can I go wrong and snagged it up. The Miata came with the full fiberglass body kit partially fit to car, a Spec Miata motor, stock tranny, Mazdacomp Spec Miata 4.30 rear end, Spec Miata suspension and an eBay header. I had a month to go before the beginning of the season so I threw the car together and ran it. Running basically a spec Miata with the windshield cut off on slicks I won the Division Championship that year and went to the runoffs and like you did this year ran at the back substantially off the pace. That was the first year the runoffs were at Road America so having an old tired Spec Miata motor was definitely like bringing a knife to a gun fight. But did I have fun? Absolutely!!! Especially if you calculate Fun per Dollar spent that season. With Mazda contingency, Hoosier tires, and the old tow fund money I actually took in more than my entry fees and fuel cost!!! (In a car that I got for free!) I ran the Ghetto Cruiser(that's her name) in that basic configuration for a number of years and continued to have a blast. I made small upgrades as parts broke, and after four years I decided to build a new motor for the last year at Road America. I bought all the right parts and got it together just in time to get on the dyno the day before leaving. It had made a funny noise on initial start up but it soon went away so we pressed on with tuning; you know, it was that "Runoffs or Bust" mentality. The car made what I thought was decent power(152hp) with stock flywheel, tranny and rear end, and running a megasquirt PNP with stock harness. So the second lap in Qualifying I let her rip and going down to Canada Corner Blammo!!! Guys behind me said it was a NASCAR style blow up :doh: Lesson Learned!!! I'm not an engine builder, at least I should have learned that lesson!!! Turns out that little noise I heard on initial startup was the exhaust valves touching the pistons and "Self Clearancing" themselves!!! The slightly bent valves lasted just long enough to ruin my runoffs. I did put a borrowed back up motor from my teammate in and ran around at the back just for the tow fund money. So the first "Real Money" that I spent on the car resulted in Disaster! I then had to pay a real engine builder to build a new motor for me. So in the space of four months that year I built two motors and spent more than what I could have bought a really competitive car for out of the classifieds!!! So going into the next year with a fresh "Pro Built" motor I was only a little bit faster. Good enough for a 9th at Laguna Seca Runoffs so I considered the season a success. I was still running the old Spec Miata suspension that came on the car, stock flywheel and stock rear end. Continued on the next year with same package and was running 8th at Daytona on Kent Prather's tail lap after lap until he finally made a mistake going into one and I got by with two laps to go for 7th----Then ran out of gas...long story! The next year running at the June Sprints(third year on motor) another Blammo! this one was not as bad, only one valve broke and immediately embedded itself in the piston, should have saved that piston cause it looked so cool. I had Jesse build me a new head and with all of my previous experience at building motors I figured I'd give it another try and proceeded to build another motor myself!!! Since the runoffs were at Mid-Ohio and Jesse's shop was on the way I decided to let him break in the motor and tune it. All was good until just after the first full pull, heard funny noise as revs were coming down. shut her down and saved the motor. Turned out that a small mis-measurement on my part resulted in a bearing starting to let go. So I became crew support and spectator at the Mid-O Runoffs. Tired of "Lesson Learning" I packed up the damaged motor and sent it to Jesse for a full rebuild. The results of both of my engine building experiences resulted in Spending Double to get the job done!!! Now I've spent more than what a top flight car could have been bought for and I still have a car with Spec Miata suspension and stock rear end ratio, I had upgraded to an alternate EMCO Syncho gear set in my stock tranny case, but am still running the stock flywheel with Spec Miata clutch. So I began last year with a fresh Jesse bullet under the hood and my old tired suspension and running gear. Podium'd every event including the Sprints heading toward Indy. Made the decision it was time for more upgrades and pulled the trigger on Jesse's Afco shock package and built a new torsion 4.88 rear end for the runoffs. Spent just a weekend trying to dial in the new set up before Indy and was starting to get a feel for adjusting shocks(never done it my entire racing career on Spec Miata Suspension)
Got to Indy with a car that drove and felt different from what I had driven for the past nine years, not bad, not great but different. Qualified 17th and would have had a good race but sustained damage on the second lap with the spinning car of McAllister in One. Drove back from the back with a wounded car to finish 18th.

What is point of this story? well there are a couple. #1 Racing on a small budget in the back can be just as fun as racing in the middle or up front. #2 R&D development is very expensive especially if you are not extremely talented. #3 buying a sorted, developed car is ALWAYS the least expensive way to potentially run up front. When you look at the top ten in FP this year, Prill, Perona, Henry, Mathis, Ruck, Hingston, Morton, Linn, Bednarz, and Kannard. they all have a couple things in common. YEARS of experience and LOTS of money spent. All ten have Top Flight cars with all aspects of the drivetrain, suspension, aero, brakes optimized and all are very capable drivers. So even buying one of these top flight cars is no guarantee that you can run up front right away, or ever.
I understand the idea of building what you've got mentality but it could be a long and hard road. It's up to you to decide if that is kind of journey that you will enjoy. I have definitely not enjoyed the lesson learning experiences as much as I enjoyed running a less competitive car on the cheap. I still enjoy the racing and have set a goal to run within the top ten next year at Sonoma. I've sharpened the knife that I bring to the gunfight but I'm still the under dog and that's OK, I kind of like it that way.
I would have to spend another $20-$25 K on my car to have everything that the front running guys have (Dogbox tranny, button clutch and flywheel, new cams and header design, stand alone EMS and ignition system, data acquisition, upgraded diff. and super light wheels). So even after nine years I would still have to spend that much to have "Everything" on my old car. Yes, you can go out and buy a top flight car for that. and that is what the "SMART" folks do. If you like the front drive cars, I think Mark Carpenter's Runoffs championship winning Integra is still available for about that much; he had it listed for years! What ever direction you chose to go in just make sure you have fun doing it, that's what we're all here for. This class is not made up of a bunch of kids looking to go pro racing, we're what the club was built on, guys that like sports cars! Guys who like working on them and racing them with our friends. The diversity of the cars is what makes the class cool and the races interesting. We all look forward to seeing you on the grid next year in whatever car you chose to campaign.

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PostPosted: Fri Dec 29, 2017 11:55 am 
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Paul, interesting overview of your recent involvement. One guy missing within your list of F prod Miata drivers from this year, Joe huffaker a guy with unlimited experience. From my perspective watching the race live at T1, Prill walked the field (yellow flags closed the field 2 maybe 3 times) from the get-go with his years of driving talent, studying data and developing with Jesse. No disrespect to anyone.

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