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A, B, or C that is the question


Kieran Gobey
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For any car a motor swap to a smaller or larger engine looks possible. If say I have a race car now 👀 and it has a 2494 cc engine... But I figure I can run just as quick with a 1895cc motor with cams because they are relatively cheap... Essentially dropping myself from C to B class. Do I get to run more competitively, or are fuel penalties and engine performance issues too big to overcome?

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I would think the points required to pay for an engine swap, plus the points for the cams, would make it unattractive to swap to the smaller motor if both made the same power. 

 

For many engines the bigger cammed smaller engine would have lower BSFC, and would thus use more fuel for the same power. The average engine speed would most likely be faster on things like pistons and valvetrain, and might reduce the durability. You would also need to regear the car, as I would guess you rpm to be 2.5/1.9 different (to run well). 

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4 hours ago, Kieran Gobey said:

right about 155... but probably not a lot more, reliably. 

 

If you're looking to be on the podium, you'll need to get whatever chassis it is down to 2000-2200 pounds as raced to be in the ball park, and hopefully whatever it is carries at least 16 gallons of fuel stock.

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5 hours ago, Kieran Gobey said:

right about 155... but probably not a lot more, reliably. 

If that is whp, that is enough.  Barely.  We won a few races with less.  Maybe won't be enough next year or 2021.

 

151 whp with 2400# car here....

Edited by wvumtnbkr
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35 minutes ago, SonsOfIrony said:

 

If you're looking to be on the podium, you'll need to get whatever chassis it is down to 2000-2200 pounds as raced to be in the ball park, and hopefully whatever it is carries at least 16 gallons of fuel stock.

 

We're working on getting our Audi up close to 150 whp, but sadly, I'm not sure how to get 400-600 lbs out of my car without removing the quattro AWD system (~300 lbs).

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8 hours ago, Black Magic said:

I would think the points required to pay for an engine swap, plus the points for the cams, would make it unattractive to swap to the smaller motor if both made the same power. 

 

For many engines the bigger cammed smaller engine would have lower BSFC, and would thus use more fuel for the same power. The average engine speed would most likely be faster on things like pistons and valvetrain, and might reduce the durability. You would also need to regear the car, as I would guess you rpm to be 2.5/1.9 different (to run well). 

Since BSFC is lbs of fuel used per hp*hr, a lower BSFC number means the engine is using less fuel for the same power. Eg, 0.45 lbs/(hp*hr) is lower and better than 0.50 lbs/(hp*hr).

 

Dropping from 2494cc to 1895cc would move you from Class C to Class A. This becomes a platform swap if your car was available from the factory with that engine, so check the specs to make sure you aren't losing something you might need, like fuel capacity or stronger drivetrain parts. 

 

It might not be worth all the effort and expense to switch, especially if you consider that Miatas and Civics are in Class A.

Edited by mender
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1 hour ago, mender said:

Since BSFC is lbs of fuel used per hp*hr, a lower BSFC number means the engine is using less fuel for the same power. Eg, 0.45 lbs/(hp*hr) is lower and better than 0.50 lbs/(hp*hr).

 

Dropping from 2494cc to 1895cc would move you from Class C to Class A. This becomes a platform swap if your car was available from the factory with that engine, so check the specs to make sure you aren't losing something you might need, like fuel capacity or stronger drivetrain parts. 

 

It might not be worth all the effort and expense to switch, especially if you consider that Miatas and Civics are in Class A.

 

Dyslexic moment. Meant to say higher bsfc (less efficient) from higher pumping losses (speed is.not your friend) and more intake charge lost out the tailpipe....

 

I assumed you were swapping a non factory engine for the car, otherwise follow menders advice.

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55 minutes ago, Black Magic said:

 

Dyslexic moment. Meant to say higher bsfc (less efficient) from higher pumping losses (speed is.not your friend) and more intake charge lost out the tailpipe....

 

I assumed you were swapping a non factory engine for the car, otherwise follow menders advice.

I knew you knew what you meant, just had to jump in. :)

 

E46 has a 2494 cc six and an 1895 cc four ...

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14 hours ago, QuaTTro said:

 

We're working on getting our Audi up close to 150 whp, but sadly, I'm not sure how to get 400-600 lbs out of my car without removing the quattro AWD system (~300 lbs).

Glad to see a TT hear  we run ours DRVOLKS.com TT last time no rear dif/ swapped tranny 5 speed ALH  for the bracket race at Thompson.  With 22 Gal of fuel driver 2800 LB and did do a trip to the dyno at the wheels real load setup 200HP 220 FTLB  at 16 LB of boost did turn it down to 10 we did run in to trouble with the engine harness ?? it would loss boost after 4 grand like a rock had to short shift it for 8 hr long day like that!!! 

3k46WOJ.jpg

0vYUP0f.jpg?1

Edited by DRVOLKS
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8 hours ago, Kieran Gobey said:

Right. The m44 is the attractive swap for the m20b25 on paper. The issue for swap is if I’m changing to the 1.8/9 m44 because that’s an e36 not an e30 engine, am I subjected to more penalties I can see in the rules yet because I’m not familiar enough?

 

Engine swaps in a nutshell.....(Most of this is in the rules)

 

You can attempt to swap any engine from a car on the VPI list. That engine specs get put in the swap calculator, which determines a point penalty based on the power. Same\less power or power below a certain power to listed champcar "weight" gets the min penalty of 50 points. 

 

If you need to do it, you have to pay for the trans with points. There is a $ limit for the engine, adapters, mounts and stuff to swap engine you need to respect. 

 

You have to start with the highest value of that chassis when doing a swap. The swap calc does this for you. You can claim any package from the car you are starting with, in your example a 4 cyl e30 or 6 cylinder, but you will be paying for the 6 cyl if you do a swap (so you can't swap in a m20 into a 4cyl e30 for less points than a stock m20 e30). You can use any e30 diff, but they expect the rest of the car to be a claimed model (4 cyl, 6 cyl etc) so you aren't really supposed to pick the best of each model to make a car that was never built. 

 

This makes an e30 with any non oem e30 motor start at 500 points, at which point you would need to ask is your 4cyl a better choice than a m50, or a 450 point m20 with mods elsewhere. 

Edited by Black Magic
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8 hours ago, Kieran Gobey said:

Right. The m44 is the attractive swap for the m20b25 on paper. The issue for swap is if I’m changing to the 1.8/9 m44 because that’s an e36 not an e30 engine, am I subjected to more penalties I can see in the rules yet because I’m not familiar enough?

This is an E30? Then you are correct, it will be considered an engine swap and not a platform swap because the factory didn't offer the M44 in the E30.

 

Your base car for this swap is the M20B25 as per rule 4.5.6:

4.5.6. Vehicles must use the highest valued model from its generation (i.e., – E30s would use the 325i as the starting point). 

 

That starts at 450 points, then add 50 points for the swap. You'll be at 500 points with no room for more mods.

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This all brings up a question for me.  Considering pre 1980 cars where the vpi chart just states pre1980 xxx points.  Based on

15 minutes ago, Black Magic said:

You have to start with the highest value of that chassis when doing a swap. The swap calc does this for you. You can claim any package from the car you are starting with, in your example a 4 cyl e30 or 6 cylinder, but you will be paying for the 6 cyl if you do a swap

So from this and I think other verbage in the vpi  or rules, in general, the points calculator accounts for the highest power combo when assigning points,  in the passage from Black Magic, highest power  4 cyl is one point number and the highest power 6 is another.  Comparing this to pre 1980 cars,  lets consider a 60's corvette or 60's mustang for reference.  Most cars in that period had a crap ton of available ratings, 67 Mustang had like 8-10 including 6 cyl's.  so the 67 Mustang is listed at 150 pts in the table with a v8 but no detail about which rating is considered.  Based on the idea that vpi automatically accounts for highest  rating, I would presume any of the three 289 ratings would be 150 pts.  Likewise I assume the 390 raitngs also 150 pts.  If this isn't the case, and I've already read posts on here that suggest you would need to "swap" to the 390, what is the accepted way to look at these old car ratings sets versus points?  They all had the same size tank and obviously the bigger the engine, the heavier the car, so going to a 390 would be detrimental in several aspects.

67 Ford Mustang ratings.jpg

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44 minutes ago, 67Mustang said:

This all brings up a question for me.  Considering pre 1980 cars where the vpi chart just states pre1980 xxx points.  Based on

So from this and I think other verbage in the vpi  or rules, in general, the points calculator accounts for the highest power combo when assigning points,  in the passage from Black Magic, highest power  4 cyl is one point number and the highest power 6 is another.  Comparing this to pre 1980 cars,  lets consider a 60's corvette or 60's mustang for reference.  Most cars in that period had a crap ton of available ratings, 67 Mustang had like 8-10 including 6 cyl's.  so the 67 Mustang is listed at 150 pts in the table with a v8 but no detail about which rating is considered.  Based on the idea that vpi automatically accounts for highest  rating, I would presume any of the three 289 ratings would be 150 pts.  Likewise I assume the 390 raitngs also 150 pts.  If this isn't the case, and I've already read posts on here that suggest you would need to "swap" to the 390, what is the accepted way to look at these old car ratings sets versus points?  They all had the same size tank and obviously the bigger the engine, the heavier the car, so going to a 390 would be detrimental in several aspects.

67 Ford Mustang ratings.jpg

 

You would get any "non special model" v8 for the 150 points, provided the engine is the exact spec that came in that year car down to the carb, intake and headers. For example, you can't claim a GM SBC 400 hp crate motor as the "same" as the 350 in a 70s vette. 

 

I don't think you will get a 428 allowed as a 150 point car :).....they made less than 700 mustangs that way a year....

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That's what I am getting at, what is the standard?  Agreed on the 428, but they made a heck of a lot of 390's.  So to the point, would the 390 be 150 points, or is 150 only the 289 or is it only one of the 289 ratings?  I guess I wouldn't consider something that would be a normal option to be special... I'd think the 390 would be a normal option just like I would think the 271 hp 289 is a normal option.  That does not mean my assumption is correct at all, and I know that. 

 

Maybe what I am asking (and not very well) is for old stuff like this how are we supposed to know which of the available ratings is the vpi directed at? And is it directed at one rating or to a family?

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10 hours ago, wvumtnbkr said:

You could go to the e30 specific 4 cylinder and call it a platform swap.

 

This would allow you a lower starting value as well.

 

That sure sounds like the obvious answer if you want a 4-cylinder E30.  300 points for an M42 or 500 for an M44, with nearly identical power stock.

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