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B230 n/a mild performance mods

sspony

sspony

Active member
Joined
May 15, 2012
Location
Maryland
Hello all,
Currently running a 1988 740 at our local rally cross events. It has a bone stock n/a b230 with an m47. My question for you is what are some mild/budget friendly changes we can make to increase performance and move power to a more usable range.
Most races are on dirt or similar and don't see speeds over 55mph. So almost always 1st and 2nd gear, rarely we'll get to 3rd. This car is for racing only and streetability does not matter. Neither does fuel economy. Currently our acceleration is a bit poor at the lower end. Would a cam swap and timing gear do much for us? Our class also requires a cat and muffler. We're running the stock pipe with stock cat and a glass pack. It exits out the side. Would a highflow cat and larger pipe do much?
 
Thats not budget friendly, takes a lot of time and bumps us way out of our class. Fun, but not practical for this application. Looking for a couple quick/cheap mods to increase power and or move it to a more usable range.
 
Waiting for someone with some experience and knowledge regarding the various cams to chime in.
 
So you're saying the low end acceleration is poor, so you want to move the power band lower? typically a stock b230 with a M cam dies over 4000rpm, I'd say you need to downshift
 
It gets stuck in the void between 1st and 2nd. 1st would spike the rpms way too high but in 2nd it's bogging slightly. Maybe a rear gear change would fix this but I feel like it needs more torque at the lower rpms. I guess that's what I meant, increasing power at the lower rpm range.
 
Shave flywheel by 7 lbs. That helps a lot.

But, be careful. More than seven or seven from the wrong places...
 
swedefiend said:
Shave flywheel by 7 lbs. That helps a lot.

But, be careful. More than seven or seven from the wrong places...
Click to expand...

Just had it resurfaced, Didn't think to have it shaved. It's a dished style. How much of an improvement and in what ways?

John, I was hoping you would pitch in. We might be willing to. What cha thinking?
 
sspony said:
Just had it resurfaced, Didn't think to have it shaved. It's a dished style. How much of an improvement and in what ways?
Click to expand...

Less rotating mass will allow the engine to be more responsive to throttle input.

Mine is NOT the "dog dish", it is the early style b21 / b23 flywheel. It was shaved 7.5 lbs but I was warned not to take any more off by the shop that did it. Structural integrity apparently questionable after taking much more.
 
Did you gut your cat out or is that checked? Bigger pipe won't do anything unless you open the head up to get more air flow out. I would think.
 
sspony said:
Just had it resurfaced, Didn't think to have it shaved. It's a dished style. How much of an improvement and in what ways?

John, I was hoping you would pitch in. We might be willing to. What cha thinking?
Click to expand...

Well follow me on reasoning...
For a given gas--pump in this case (whatddya get out there? 92 okt? or 93?) --- torque is pretty much related to engine volume and dynamic compression

So, if you're willing to pull the head--and mill it 050 or 060"..you bop the compression up and have instant more torque from that..

THEN maybe think of a cam profile that is intended to be used for what you're doing, not some Volvo emissions cam....a cam intended for fun.

Here's one I'm going to get for a street car for my wag-goon:

KY 1212 112grader nockvinkel 12,2mm lyft 287dur vid k?rspel, Popul?r profil f?r lite h?ftigare turbo +500HK
Kan k?ras p? gata


That's 112 lobe center, 12,2mm lift, 287 degrees duration with normal lash
Popular profil for little heftier turbo
Can drive on road.

or KY112 110grader 280dur
11,2mm lyft TDC lyft 2,5mm
Sn?llare profil som ?ven fungerar mycket bra till personbil 1000:-
KY 112N3
Samma profil som ovan men slipad p? nytt std B23 ?mne
(inget inbyte beh?vs) inkl laschcaps 1695:-
KY 112N30
Samma profil som ovan men slipad p? nytt std B230 ?mne
(inget inbyte beh?vs) inkl laschcaps

110 lobe centers 280 duration
11,2mm lift TDC lift 2,5mm
"Kinder" profile which even functions very well to road car
The blue one says "same as above but ground on a new standard B230 core (no exchange needed) incluse lashcaps

Thats $200...They will send by mail..I'm getting 2 for B230 and one B20 cam
 
So your saying pull the head, mill it, install a hotter aftermarket cam, and run 92 or 93 octane.

What's the most aggressive stock cam that could be run without pulling the head and such? And would it really change anything without bumping compression up?
 
sspony said:
So your saying pull the head, mill it, install a hotter aftermarket cam, and run 92 or 93 octane.

What's the most aggressive stock cam that could be run without pulling the head and such? And would it really change anything without bumping compression up?
Click to expand...

If you mill the head that much, you're raising the compression ratio, which is the reason the cam change will help torque significantly instead of simply idle poorly for style points.
 
sspony said:
So your saying pull the head, mill it, install a hotter aftermarket cam, and run 92 or 93 octane.

What's the most aggressive stock cam that could be run without pulling the head and such? And would it really change anything without bumping compression up?
Click to expand...


There's an rigid relationship between compression ratio and "event duration"..And the particular event that has a direct bearing on compression ratio is:
when does the intake valve close after the crank is at the bottom also known as BDC bottom dead center.

Take some complete snooze cam like any Volvo emission cam----> that one in my wag-goon..

fukit we'll post this again cause it helps visulize the problem:
69_6cyl_cam.gif


Notice where it says INTAKE CLOSES (51.5 degrees) AFTER the crank is at BDC and the piston is going up..
Well from bottom to top the crank turns exactly 180 degress, right?
And the boring limp dick cam has the intake valve open for damn near 1/3 of all the crank rotation there is.
(now piston motion is not in any way linear but don't worry about that,)
If the valve is OPEN then so solly lound eye but it means there's a HOLE to the outside world and you are not making compression...until the valve closes..

So the way 99% of all the pro engine builders on Forum-land talk about compression.
Like this guy
maxresdefault.jpg


Is only a theoretically "ideal" number....
In reality you don't begin to make compression till later--when the valve closes..

Now a "hotter cam" opens the valve a bit earlier and opens it faster, and higher maybe and closes it later..

Wait. Closes it later? yeah which mean your crank has rotated more and the piston has gone up more before you even start making compression.

So milling the snot outta the head is done so when you begin later to make compression you have something in the time you have..To compensate for the later closing..

Got it?
 
Here's some fun stuff.

Number of Cylinders :
1
Bore in Inches :
3.78
Stroke in Inches :
3.15
Rod Length in Inches :
5.98
Static Compression Ratio : <------made up just as an example and as a constant in the calculation
10:-)1)
Inlet Valve Closes ABDC :
55
?
Boost Pressure in PSI :
0
Target Altitude :
0
(Feet)
Calculate

Static compression ratio of 10:1.
Effective stroke is 2.62 inches.
Your dynamic compression ratio is 8.49:1 .
Your dynamic cranking pressure is 172.68 PSI.
Your effective boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of 0 PSI is 8.49 :1.
V/P (Volume to Pressure Index) is 15

Changing just the intake closing to say 65 degrees ABDC

Static compression ratio of 10:1.
Effective stroke is 2.41 inches.
Your dynamic compression ratio is 7.89:1 .
Your dynamic cranking pressure is 157.03 PSI.
Your effective boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of 0 PSI is 7.89 :1.
V/P (Volume to Pressure Index) is 13

Just as an example here's cam data on a Ford Pinto "fast road" cam (remember I'm a Ford guy really so its easier to find in Engrish for you
FR32 FAST ROAD
Rev range2500-7000
Cam lift....275? .
Valve lift455? .442?
Duration285? 280?
Intake opes BTDC.....34/ closes ABDC.....71
Exhaust opens....... 68/closes.......32
Duration @ 1mm lift...240?
Lobe centers...............108? .
Valve clearence........010? .012?
Valve lift @ TDC..........086?
16bhp approx. increase
Click to expand...

That a mild cam and it close intake at 71* ABDC

See? we have to compensate or its a waste of time and the cam doesn't work and you get no POP!

No just for fun lets go back to the second example with the mild cam and see what we'd get if you had a "static compression" of 11.6:1 (which is NOT crazy with aluminum head..I do 11.3 in my cast iron stuff)

Static compression ratio of 11.6:1.
Effective stroke is 2.41 inches.
Your dynamic compression ratio is 9.11:1 .
Your dynamic cranking pressure is 189.07 PSI.
Your effective boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of 0 PSI is 9.11 :1.

Wow a whopping 9.1...
Is this clear?
 
Wow John, this is outstanding information. At first glance it all makes sense, now give me a few minutes to re-read and process it all haha.
 
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