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#1 |
Board Member
Join Date: Dec 2008
Location: Seattle
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![]() Hi all have a 93 + b230ft motor i want to get going a little bit.
I was thinking a bigger turbo than stock and an ipd cam. My shop teacher also suggested i raise the compression ratio. What do you guys think should i raise it a bit? any big trade offs?
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1983 flathood 242 Turbo, IPD Turbo Cam, Adjustable Timing Gear, IPD 25/22 Sways, Bilstein Shocks ![]() |
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#2 |
Board Member
Join Date: May 2006
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![]() I wouldn't. There are better things to spend your money on IMO
Last edited by Tom Wiley; 05-28-2010 at 12:48 AM.. Reason: can't read |
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#3 | |
Board Member
Join Date: Mar 2006
Location: Virginia Beach, VA
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![]() Raising it is supposed to give you better off-boost torque, but it is said to lower the detonation threshold. That being said, people +T the normally aspirated B230F's all the time, and they've got a 9.8:1 CR vs. your 8.7:1.
I'd say raise it to 11:1 and keep stock boost level with some headwork, get some bigger injectors, and drive lightly while the ECU learns the new setup.
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Quote:
![]() 1970 Volvo 164 M400, Virgos, Dual Webers, and A/C?! 1990 Volvo 745GL 278,000 Miles No turbo, automatic. Regina with T cam. Too much traction. |
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#4 |
Board Member
Join Date: Aug 2006
Location: sanction rescinded
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![]() Raising the SCR from where that motor is now is not necessarily a problem, IF you go about it intelligently.
True: raising the SCR does tend to lower the detonation threshhold. Which is why that motor is about 8.7:1 from the factory, rather than the higher than 9:1 ratio the NA motors were built at. If you want to raise the SCR 'some', AND raise the detonation threshhold at the same time, then the way to go is to do the things needed to make your motor 'tight squish'. ....and the way to do that is to measure the piston deck height [done with the cyl head removed] to see how positive the deck height is. That motor ['93 and newer B230FTs] is very likely to have positive piston deck height of about 6 thou [0.006in]. i.e., the pistons top out at TDC about 6 thou above the block deck. You have to measure and confirm the piston deck height. You do NOT ASSume what the piston deck height is: you measure it. THEN, you order the correct thickness Cometic MLS HG that will result in giving you a piston to cylinder head clearance somewhere between 30 thou and 35 thou. ...usually a 36 thou MLS HG will do the job quite nicely. Read up on the subject of 'tight squish'. It works. You'll also need a way of adjusting/correcting the camshaft timing. i.e., an adjustable or re-indexable timing gear for the camshaft. Otherwise, going tight squish via a thinner HG will retard the camshaft timing, which is not helpful usually. At least one heat range colder spark plugs is also required. I run two heat ranges colder. TF |
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#5 | |
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Join Date: Jul 2004
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![]() Quote:
But, when I raised the SCR on my last b230ft build I tried to stay ~9:1. I wouldn't recommend going past 10:1 on anything not using race fuel or water injection if using a turbo as well. |
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#6 |
Exklusiv Zubehör Klub
![]() Join Date: Sep 2002
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![]() The other consideration is that while you can increase the SCR quite a bit if at the same time you bring the dynamic CR back down via more cam, you can only go so far if you have no means of adjusting your timing curve. You need to increase the turbo size at the same time as well since the additional overlap will hurt performance if you are not reducing backpressure at the same time.
it's a tricky balancing act when take to the extreme, but something in the 9-9.5:1 area with soemthing like a K cam and an 0.63 hotside is a good combo |
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#7 | |
Board Member
Join Date: Jul 2009
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![]() Quote:
N/A race engines that are able to breathe well but use more extreme cam timings can use even higher arithmetic CRs... around 12.5:1 is common... but that has nothing to do with a turbo application. Where cam timing has far less influence on VE such long duration intake periods aren't needed, and a late closing exhaust valve is definately not required, so the CR should be correspondingly lower. Even on a low-boost application I'd be reluctant to go very much above 9:1 At the other extreme a really serious race turbo motor might rely heavily on boost for cylinder filling at higher rpm, and a much lower arithmetic CR will give a smaller reduction in cylinder pressure per degree of crankshaft rotation for the same peak cylinder pressure, and therefore a greater effective pressure and at larger crankpin angles producing more torque. These sort of engines can run CRs as low as 6:1, but in combination with a high boost threshold off-boost performance is very poor. A higher arithmetic CR would no doubt improve off-boost performance and fuel economy, but will ultimately limit the usable boost pressure. You've really got to build the motor to suit your own needs, but I can't see this being a situation where a CR of anything like 11:1 would be advisable! |
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#8 |
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Join Date: Jul 2004
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#9 |
Unnaturally Aspirated
Join Date: Feb 2004
Location: Elk Grove
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![]() That's what a +T is. You can raise the compression around a point by putting an NA block under all that turbo stuff. Drill the return hole out, add an oil feed from the front of the block. Only $100 or so for a short block from pick and pull. Dollar for dollar, raising the compression ration for the cost of a cheap cam is a good bang for the buck (much pun intended). Though at that point you are producing enough squish to go bang.
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~Steve O "Cleverly Disguised As A Responsible Adult looking for cracks in the glass ceiling" '94 965 For Sale $1400 before smog '80 242 Sold '61 P1800 Sold '95 Dodge Dakota wife's redneck caddilac '87 760T Scrapped '90 740 SE F+T 13.962 @ 100.5 1/4 ~ Daily Driver |
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#10 |
Backwards Turbo
![]() Join Date: Feb 2005
Location: Göteborg, Sweden
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![]() With tight squish, large duration cam, large turbine housing and header, and methanol injection I'm running 20psi on my 10:1 B230F+T with no audible detonation.
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#11 |
Board Member
Join Date: May 2006
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#12 |
I sell Volvo parts!
Join Date: Mar 2004
Location: Seattle, WA
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#13 | |
...
Join Date: Jul 2004
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![]() Quote:
With or without ability to datalog. Your choice ![]() |
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#14 |
I sell Volvo parts!
Join Date: Mar 2004
Location: Seattle, WA
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![]() I was asking Poik what he uses - I am aware of Knocksense and have it installed on one of my cars...
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#15 |
Backwards Turbo
![]() Join Date: Feb 2005
Location: Göteborg, Sweden
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![]() I use knocksense tied into megasquirt, so if it knocks it will pull timing.
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#16 |
The Beloved Oarnge Juice
![]() Join Date: Aug 2009
Location: WA
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![]() as mentioned....static and dynamic are two different things and cam choices affect it alot.
my 91 b230ft with ipd cam all stock with 8v head cranked 145psi same engine now stroked to 2.5l.....16v head with stock cams.....rsi 16v pistons im cranking a little over 210psi mathed out the static is supposed to 8.5-1 but cranking sure did go up. i have some adjustable gears coming to help dial this out and will get turbo cams ground one of these days for this motor. |
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#17 | |
Never go full retard.
Join Date: Mar 2007
Location: Los Angeles
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![]() Quote:
__________________
Fake Race Car |
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#18 |
Exklusiv Zubehör Klub
![]() Join Date: Sep 2002
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![]() 210 on an 8.5:1 motor doesn't even make sense to me, even with next to no overlap... I have my doubts it's 8.5:1 but that's just me.
![]() Typically you'll use cam gears to effectively increase the LSA on a set of NA cams, which actually makes DCR higher. Using my own twin cam motor as an example: With 960 cams at 0/4 my 8.5:1 motor cranks ~170. At -2/4 it cranks ~180. That's an increase in LSA of 6 degrees vs. straight up, and a more appropriate setting for turbo (at least in my case, as the motor makes more power everywhere at -2/6) . I don't understand Karl's leakdown reference... |
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#19 | |
ALDORF THE DESTROYER OF WHITE SHIRTS
Join Date: Sep 2008
Location: Western PA
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![]() Do you worry about it not being able to detect knock above say 4000 ish rpm? I know the miata guys I know say they can't detect much above 4000 because the engine is so noisy (they also mount the knock sensor for KS on the bottom of the engine because I guess that's where mazda put it in later years that had one), so they basically completely ignore it above 4500. Is this an issue we also have on the volvo or is that part of the BP engine being a horribly noisy engine or if anyone has even looked into it.
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ovlover: Its an auto. Problem found, Manual swap. Problem solved Quote:
I AM ALDORF THE DESTROYER 1985 744ti M46 -3rd, 15g, 3" exhaust, Ported Head, 333,333 miles 91 945 Turbo 3 pedal auto, DD 83 242 Turbo Flathood 15 Golf TDI 6 Speed Doug <3 me. Not scottyd. doug was here again |
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#20 |
Backwards Turbo
![]() Join Date: Feb 2005
Location: Göteborg, Sweden
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![]() Above 5k it's a lot of static with a loud exhaust so I have MS ignore anything above that. If it's going to knock it is most likely going to knock around torque peak, which is about 4k on my engine.
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#21 |
Backwards Turbo
![]() Join Date: Feb 2005
Location: Göteborg, Sweden
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![]() And yeah 210 is pretty high.. My 10:1 +T with IPD cam was 180.
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#22 |
Never go full retard.
Join Date: Mar 2007
Location: Los Angeles
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#23 |
BRANDSCHUTZVORSCHRIFTEN!
![]() Join Date: Dec 2002
Location: mont, AL
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![]() I had 205-210 with my b230f back in the dizzay. I haven't checked it on any of my 16v motors, stopped caring about that a while ago. if it doesn't sound 'off' while cranking, and it runs out good, meh.
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"They bum rushed them in their own crib, they drank all their beer, they partied with their ladies and they left with the trophy" Now with in-house Dyno tuning! Megasquirt Tuning! Plug and play LH 2.4 Megasquirt, now with stealth mode! |
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#24 |
The Beloved Oarnge Juice
![]() Join Date: Aug 2009
Location: WA
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![]() i used adverised numbers from the rsi pistons....compressed elring and advertised 16v combustion chamber and ran it through a calculater. 2 different ones gave a close 8.5 to 1 motor. i was seeing if using a cometic and going to tight squish would work but then you mentioed that the 16v dont have enough squish area to worry about so i went elring.
the cranking does seem high but it is what it is....nothing fancy in my motor but more stroke. initial cranking was 180psi before start and now with 600 miles its rockin the 210 number. |
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#25 |
Board Member
Join Date: Jan 2007
Location: End of Earth-North Dakota, USA
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![]() How come nobody welds in material and creates clover leaf shaped combustion chamber squich pads?
__________________
![]() 72 1800e, (74 B30f, M410, 1031 w/3.31:1, Weld Draglite 10x15/ 12x15, 265/50-15/ 295/50-15 BFGoodrich TA radials) http://www.youtube.com/watch?v=AKn-LTNa4rc Top Speed Attempt Video http://www.youtube.com/watch?v=T3qDGChRDDY Weather Report "Nubian Sundance" |
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