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PostPosted: Tue Dec 26, 2017 4:43 am 
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Posts: 140
All:

I turn, once again, to your great wisdom! Based on much of the information that I have gathered from my previous request, the Saturn is down SIGNIFICANTLY on power. As such, I need to do something the rectify this problem (aka spend much $$$ and get proper power). However, before doing so, I did some comparisons to try to understand if I can truly compete. What I have found has me a bit concerned and I wanted your input.

FP Miata: 1597cc engine, 55mm Throttle Body size
Acura Integra (90-93): 1835cc engine, 58mm Throttle Body size
Honda CRX si (88-91): 1590cc engine, 58mm Thottle Body size
VW Golf GTI (90-92): 1984cc engine, 61mm Throttle Body size
Saturn DOHC (91-95): 1901cc engine, 50mm Throttle Body size

My concern, as you can see from the data above, is that the stock throttle body size will not allow enough air into the engine to be competitive. I have tried to run some of the "online" calculators to determine what the maximum airflow would be, but have not yet found one that made sense.

Hoping to get some input on whether this will be a bottleneck and I should consider other options or that this is not a concern and to charge forward.

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Bill H
92 Saturn SL2 - SCCA F-Production


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PostPosted: Tue Dec 26, 2017 6:24 am 
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Joined: Thu Jan 22, 2004 3:31 pm
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That's a 90mm stroke by 82mm bore. Probably never going to be a high revving engine. Should make lots of midrange torque based on the stock HP and TQ numbers. Gotta ask, why reinvent the wheel. Are there performance parts out there made for this engine I don't know about? And if not maybe there's a good reason why. If so ask those that have built them. Maybe a Saturn performance forum.


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PostPosted: Tue Dec 26, 2017 7:11 am 
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There are not performance parts available because Saturn never released the ECU for modifications by the aftermarket. Without the ability to tune the ECU, it became very difficult to build power. In Prod, this is not a problem (already changed to aftermarket ECU).

I am just concerned that the 50mm throttle body will be too big a restriction to built enough power to compete...

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Bill H
92 Saturn SL2 - SCCA F-Production


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PostPosted: Tue Dec 26, 2017 7:18 am 
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Joined: Tue Dec 31, 2013 10:40 am
Posts: 271
Location: Huntsville, AL
Out of curiosity, why did you choose this car/engine package to run in FP? Was the car an ex IT car and this seemed like an "easy" button? What advantageous combination of parts in the standard road car drew you to this particular chassis?

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Brett W
Huntsville, AL


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PostPosted: Tue Dec 26, 2017 7:30 am 
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Joined: Sun Nov 08, 2009 12:58 pm
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Location: SJ
planet6racing wrote:
There are not performance parts available because Saturn never released the ECU for modifications by the aftermarket. Without the ability to tune the ECU, it became very difficult to build power. In Prod, this is not a problem (already changed to aftermarket ECU).

I am just concerned that the 50mm throttle body will be too big a restriction to built enough power to compete...



If you think in terms of a 50mm Single Inlet Restrictor, it will support a lot more power than you could possibly make in FP. Your cylinder head will do more to hold you back than the throttle body. Have you had your head on a flow bench? Have you experimented with valve seat angles and valve head shapes?

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Bob A.


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PostPosted: Tue Dec 26, 2017 8:19 am 
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Location: Wauwatosa, WI
Holidays vacation, Happy Holidays info. :mrgreen: Don't know where your other parts of engine are but to answer your question it would appear you could do the following for low buck while not being legal.

Geo Storm the big boy DOHC It's called car-part.com/cure the details including bore the intake manifold and get to the dyno. Scroll down and there is dimensional data for the Saturn, Geo SOCH and DOHC throttle body plates. Years back there was a quick as I recall Saturn don't remember the class which raced at the Farm from MI. Dark green and silver. http://saturnpioneer.webs.com/geostormtbswap.htm

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David Dewhurst
CenDiv Milwaukee Region
F Prod #14


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PostPosted: Tue Dec 26, 2017 9:39 am 
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Joined: Sun Dec 14, 2014 11:06 pm
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Location: Portland, OR
Crx = 55mm

Or did 58 come from David’s car-part.com recommendations? :think:

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Ian
FP CRX Si


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PostPosted: Tue Dec 26, 2017 11:47 am 
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Location: Wauwatosa, WI
Ian, for a bolt on piece with some other help.

INLET inch - OUTLET inch- DISC mm=

Stock S-Series 2.07 2.05 2.00 = 50.80mm
SOHC Geo 2.55 2.10 2.09 = 53.09mm
DOHC Geo 2.55 2.22 2.14 = 54.36mm

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David Dewhurst
CenDiv Milwaukee Region
F Prod #14


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PostPosted: Tue Dec 26, 2017 1:51 pm 
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Joined: Mon Jan 05, 2015 8:45 am
Posts: 140
Brett W wrote:
Out of curiosity, why did you choose this car/engine package to run in FP? Was the car an ex IT car and this seemed like an "easy" button? What advantageous combination of parts in the standard road car drew you to this particular chassis?


Easy answer - because I'm an idiot. I had one and decided to build it for IT. At the time, there were a couple of people campaigning them and doing well, but they worked for Saturn and had access to resources that mere mortals do not...

hoffman900 wrote:
If you think in terms of a 50mm Single Inlet Restrictor, it will support a lot more power than you could possibly make in FP. Your cylinder head will do more to hold you back than the throttle body. Have you had your head on a flow bench? Have you experimented with valve seat angles and valve head shapes?


OK, good. Thank you. I've not done a full head development, yet - starting to plan (and save) for that but did not want to chase that if the TB was going to be the show-stopper.

Ian Green wrote:
Crx = 55mm

Or did 58 come from David’s car-part.com recommendations? :think:


58 came from a google search and review of what I believed to be credible sources. I found 58mm in (2) different places and thought it was correct - sorry about that!

David Dewhurst wrote:
Ian, for a bolt on piece with some other help.

INLET inch - OUTLET inch- DISC mm=

Stock S-Series 2.07 2.05 2.00 = 50.80mm
SOHC Geo 2.55 2.10 2.09 = 53.09mm
DOHC Geo 2.55 2.22 2.14 = 54.36mm


Dave - please quote chapter and verse from the GCR that will allow me to change from the stock Saturn throttle body. I will not violate the GCR - sets a really bad example for my kids!

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Bill H
92 Saturn SL2 - SCCA F-Production


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PostPosted: Tue Dec 26, 2017 2:16 pm 
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Joined: Thu Oct 03, 2002 10:34 am
Posts: 2804
Location: Wauwatosa, WI
David Dewhurst wrote:
Don't know where your other parts of engine are but to answer your question it would appear you could do the following for low buck while not being legal.

Geo Storm the big boy DOHC It's called car-part.com/cure the details including bore the intake manifold and get to the dyno. Scroll down and there is dimensional data for the Saturn, Geo SOCH and DOHC throttle body plates. http://saturnpioneer.webs.com/geostormtbswap.htm


Bill, per my first post, "but to answer your question it would appear you could do the following for low buck while not being legal". If you truly want an answer to your original question throttle body size, it's pretty well laid out for you. Here's another article for you to compare your engine to. http://www.teamscr.com/motorsports/tech ... power.html It's a 150 hp ITA saturn, dyno graph included. There's a couple names you could contact within the article. Do your today hp torque numbers equal this ITA engine? I've openly done illegal things along the way with my race car for a learning process and my 2 boys and 3 grand kids are none the worse. Lighten up, the dyno doesn't recognize legal or illegal modifications!!!

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David Dewhurst
CenDiv Milwaukee Region
F Prod #14


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