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PostPosted: Tue Dec 26, 2017 6:29 pm 
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Dave:

Very familiar with James' work and what he acheived. That was 150HP at the crank - with the typical losses I am right in the same neighborhood. However, this is not nearly enough to compete with the people up front who are well north of 150HP to the wheels...

I know there is a ton of development work to be done - just wasn't willing to pour cash into the engine if there wasn't a prayer of getting there due to incoming air restrictions...

And, as far as lightening up, it's pretty hard to do this time of year. All those damn cookies and candies and such... :D

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Bill H
92 Saturn SL2 - SCCA F-Production


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PostPosted: Wed Dec 27, 2017 5:15 am 
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The 1.8 EP miata also uses a 55mm TB...


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PostPosted: Wed Dec 27, 2017 5:31 am 
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planet6racing wrote:
Dave:

Very familiar with James' work and what he acheived. That was 150HP at the crank - with the typical losses I am right in the same neighborhood. However, this is not nearly enough to compete with the people up front who are well north of 150HP to the wheels...

I know there is a ton of development work to be done - just wasn't willing to pour cash into the engine if there wasn't a prayer of getting there due to incoming air restrictions...

And, as far as lightening up, it's pretty hard to do this time of year. All those damn cookies and candies and such... :D



I honestly would be looking at valve size to determine its power potential. An engine doesn't care if it's getting its displacement from bore size or stroke - displacement is displacement (calculate the piston CFM demand, 1.9L is 1.9: no matter how you get it). However, what a smaller bore results in are smaller valves. Any perceived torquiness (is that even a word?) due to a larger stroke engine is because the smaller valves choke earlier, thus the power curve is pushed down vs a larger bore / larger valve combination. Looking through the GCR real quick, the intake valve is larger than most of the Hondas and the Miata, but it again, it does have more displacement.

Go through the GCR and calculate valve area as it compares displacement and you'll get a better picture of what you have.

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PostPosted: Wed Dec 27, 2017 9:01 am 
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You might want to throw some science at it. Three ways to do this that come to mind -

1. Flow bench - it would not be terribly expensive to pay someone to flow head+manifold+throttle body vs just head+manifold and a radiused inlet or a bigger throttle body (or both). Needs some thought as to what to do with the answers but would give some numbers.

2. Computer simulation - I've used the Performance Trends Engine Analyzer application to advantage. Getting the model right needs some technical savvy and trial and error but once dialed in it models changes pretty well. This also works great in conjunction with the flow bench results from above.

(I modeled my VW Scirocco engine in ITC trim and tweaked the model to fit the known power output. It has done a very good job of predicting the power and curve shape in HP trim, and also a very good job of modeling my similar but bone stock 1.8 GTI Rabbit engine (vs chassis dyno pulls in both cases). Having a "starter" engine of known power with which to tweak the model so that simulation matches reality is a huge advantage)

3. Dyno - as David suggests, can you get a bigger throttle body kluged on and try back to back dyno tests? Or just run wot on track or dyno and measure manifold pressure - that will give an idea of the pressure drop from atmosphere to plenum, most of which is likely drop across the TB assuming that is the smallest cross section.


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PostPosted: Wed Dec 27, 2017 10:58 am 
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I use EngMod4t for engine simulation work and I do some simulation for other people.

Some keys:

1) You need a baseline engine with known dyno results
2) To create your baseline you need Cam Dr (or S96 files, or whatever) for whatever cam was in the engine for the baseline. The data will have to be calculated at the valve. More on this later.
3) You absolutely need flowbench numbers
4) Very accurate measurements of everything.

You build the model and test. It should be close, but you may need to tweak the burn model a little to get it to match up. Then you can make changes.

For any camshaft change, you'll again need actual valve lift measurements. Again, this must be taken from the valve - which will require measuring your entire valvetrain accurately and then multiplied through by the lobe lift. It's not as simple as just multiplying through with the rocker ratio. What happens at the lobe and what is actually happening at the valve may not be what you think. With a OHC rocker type engine, if the cam lobe isn't for that exact application, your valve lift curve will not be what you think it is as the rocker ratio will change through the curve. This goes for pushrod engines to a lesser degree. If you take a valve lift curve and divide it by the lobe lift curve - you'll see how rocker ratio changes throughout the lift curve.

Any change in valve size or port configuration will require measured data from a flowbench.

The only thing I'm willing to change in a simulation are tune lengths - both exhaust and intake. Anything else will require remeasurement.

I took ten minutes to make a quick spreadsheet of just some combinations I picked out of the GCR:
Make | Model | Prep Level | Intake Valve Area / Displacement (/ cylinder) (as a %)
Saturn | SL2 | 2 | 8.544
Mazda | Miata | 2 | 9.41
Acura | Integra (90-93) | 2 | 8.15
BMC | Sprite/Midget (1275) | 1 | 6.74
Fiat | 124 Spider | 1 | 6.78
Ford Capri | 1 | 6.94
Triumph TR4/3 | 1 | 5.70
Honda Civic SI (88-91) | 2 | 8.21

I have no dog in this fight, so I have no interest in taking this further (other than the ten minutes I spent). Of course, the above is just a simple way of looking at things and discounts things like how good the manifold and the rest of the head is. It doesn't tell the whole story either as valve lift for the Level 2 stuff is restricted. Yeah, the Miata has more valve area per displacement, but it's also limited to .390" valve lift as opposed to the .450" valve lift of the Saturn and Hondas. With that information, you could calculate valve curtain area for each combination, but that's somebody else's fight.

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PostPosted: Wed Dec 27, 2017 12:34 pm 
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planet6racing wrote:
Dave:

Very familiar with James' work and what he acheived. That was 150HP at the crank - with the typical losses I am right in the same neighborhood. However, this is not nearly enough to compete with the people up front who are well north of 150HP to the wheels...

I know there is a ton of development work to be done - just wasn't willing to pour cash into the engine if there wasn't a prayer of getting there due to incoming air restrictions...

And, as far as lightening up, it's pretty hard to do this time of year. All those damn cookies and candies and such... :D


Bill, I am very impressed with your enthusiasm for this project and not trying to be a "downer". I too really enjoy racing something that is unique, that you develop yourself, and that you can't just buy parts and development somebody else did for. Sadly I have also seen enthusiast go down this rabbit hole only to burn out in the end because they didn't fully comprehend how far they have to go. My light Fprod full prep rwd car makes 140hp AT THE WHEELS and is 15-20% down on it's competitors. There are FWD H production cars that make way more than the 150HP at the crank you reference. I think your project and your enthusiasm are really cool. Just make sure you understand how far you are from "fully developed", can enjoy the journey, and will be ok if you get there and are still not competitive.

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Curtis Wood
F prod Alfa Spider
curtisATthiscrazygarageDOTcom


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PostPosted: Wed Dec 27, 2017 7:17 pm 
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Curtis wrote:

Bill, I am very impressed with your enthusiasm for this project and not trying to be a "downer". I too really enjoy racing something that is unique, that you develop yourself, and that you can't just buy parts and development somebody else did for. Sadly I have also seen enthusiast go down this rabbit hole only to burn out in the end because they didn't fully comprehend how far they have to go. My light Fprod full prep rwd car makes 140hp AT THE WHEELS and is 15-20% down on it's competitors. There are FWD H production cars that make way more than the 150HP at the crank you reference. I think your project and your enthusiasm are really cool. Just make sure you understand how far you are from "fully developed", can enjoy the journey, and will be ok if you get there and are still not competitive.


Thank you, Curtis. I've been travelling this rabbit hole for quite some time with full awareness. The tipping point has been the classifieds that have been posted recently, especially that Toyota Paseo GT3 car... The wife says it is a "skosh" high - still trying to figure out what she means!!!

Thank you to everyone else for the other ideas. I like the idea of simulation - as an engineer by training, that makes the most sense. I've got some homework to do and some dyno pulls to make in order to calibrate the models. Then I can at least get some good estimates of what is possible within the ruleset (come on 375HP! :D). I know the only shortcut is cubic dollars, so I am prepared to take the time and develop the car... Well, I think I am.

PS: Anyone know of a really good head person that is super easy to work with? (I know Jesse is the easy button - just wondering if there is anyone else.)

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Bill H
92 Saturn SL2 - SCCA F-Production


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PostPosted: Wed Dec 27, 2017 9:21 pm 
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Since the Saturn was supposed to be a copy of Hondas whole small car process, time to see if GM could even copy the good parts of the Honda program correctly.

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PostPosted: Thu Dec 28, 2017 1:14 am 
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Bill, i know a guy who is a fantastic cylinder head guy and great to deal with, but he’s more interested in Level 1 type builds. For those that need someone like that, here is his contact.

Nick Smithberg, Smithberg Racing: http://www.smithbergracing.com

Len Hoffman is around on these forums and he does a lot of IT (Level 2) prep heads for racers in the SE.

Len Hoffman, Hoffman Automotive Machine: https://newsite.hamheads.com

No experience, but I know some are using Jim Stewart. He also does a lot of SMiata heads.

Jim Stewart, Stewart Engines: http://www.smart-series.com/pages/stewart.php

Aaron Kelly builds a killer MG head and does a lot of work on circle track stuff. Not sure if he’s interested in a Level 2 head. Look up AVPHeads on here.

What you really need is a good camshaft and exhaust guy.

Jesse has access to the back door to Megacycle (Jim Dour) and they’re a great cam grinder to have in your circle. You may want to talk to someone about converting your hydraulic buckets to solids. Jesse pointed abkut maximizing the lobe area in his Sportscar article (which Level 1 and Level 2 builders should be doing). With a direct acting bucket, velocity is a function of the diameter of the bucket (and how close you want to run the lobe to the edge - it’s just a giant flat tappet). The game lobe designers play is all about maximizing velocity as fast as they can while trying to minimize the acceleration peaks.

If no one has lobes designed for your bucket diameter and these lift rules, this could get expensive fast. Lots of people use Web, and they have a big catalogue of lobes, but they’ll probably just pick something out that’s close enough and may not be maximized. Of course, I’m talking 10/10s here.

Other lobe designers I can think of that will work with a DOHC set-up:
Hans Herman - of ‘80s BMW F1 game
Dan Crower: http://danielcrowerracing.com
Mike Jones: http://jonescams.com
Dimitri Elgin: http://www.elgincams.com

Of course there are others, and the big guys (Comp, Crane) are certainly capable, but good luck getting a hold of anyone who would be of any help.



Exhaust, there are a few that get it. Calvin Elston is the granddaddy of modern tri-y header design. He introduced the 4-2-1 to NASCAR, but has wins / records / Championships (with both tri-y and other designs) in NASCAR, World of Outlaws, LeMans, NHRA, Grand Am, and just about any other big pro series in NA. He’s semi-retired, but still takes on work. Make the collector adjustable so you can fine tune things on the dyno.

Calvin Elston, Elston Headers: http://elstonheaders.com

All this won’t be cheap, so you need to solicit other opinions than my own and shop around. I’m sure Jesse is a busy guy, but a phone call to him would be worth it.

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PostPosted: Thu Dec 28, 2017 5:36 am 
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Reading this thread with interest. Much more interesting than most!

Really good points throughout this thread. Obviously with a more common engine build such as a Miata or Honda you can rely on experience from past builds and builders. With a one off build you have to be willing to spend money on research and development. While the simulation is good, I've never seen it be accurate enough to actually optimize the specs of the build to the tee. You'll end up with many cam grinds, which is where your power will come from, and potentially many different header systems. If your willing to sink another 15k into your engine program you'll probably be pretty competitive engine wise. Now, how is the car? What is the suspension like? What shocks are you running? A guy can spend another 10k in chassis development without blinking.

To Curtis' point, this is why most people pull the easy button so they can have fun going racing in a known commodity. If you enjoy development more than racing up front in the near future, then you should go for it. I'd rather see you stay in Prod than go GT racing of course and there are always great prod cars for sale for less than you'd spend on making your car competitive. When I see an SIR I vomit in my mouth just a little. :(

If you'd like to develop a program I'm always willing to help. You have to remember, in limited prep we can't port and develop the head like in level 1, so the flow of the head will really determine the potential of the engine, however, the intake manifold can also make a big difference and honestly for a 1.9l engine that 50mm throttle body worries me a bit. Certainly you will be rpm limited which isn't a bad thing as long as we can get enough air in the engine down low. I'd envision a torque monster engine which is good for getting out of corners but depending on gearing and high lift flow, you may have some trouble down the longer straights.

Thanks for the interesting thread, we've needed one of these!

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