• Hello Guest, welcome to the initial stages of our new platform!
    You can find some additional information about where we are in the process of migrating the board and setting up our new software here

    Thank you for being a part of our community!

Engine Vac at idle too low, how to fine tune MS and B230

thelostartof

unbalanced chemical
300+ Club
Joined
Jun 26, 2002
Location
Apache Junction, AZ
Ok so here is my problem, my brakes suck, the first stab when driving is great, all of that wilwood greatness but after a bit of being on them or the second time i get on them they just straight up suck, after going over a new brake booster, an added vac can to help increase capactity it just still sucks. Cold start is the worst, trying to stop the thing at slow speeds is just no power brakes at all which I firmly believe is becaues of the lack of engine vac. I am sure the age of the pads and rotors could be an issue but from my point of view the lav of engine vac is 99% my issue as the rock hard pedal is my issue.

Warm running I get around 5-8in and under cruse i can see 12-15ish. I am a bit fried in the brain from life to make senes of what I need to tweak and check to get the most out of my engine timing at idle to get vac back where it should be. I am almost to the point of just getting an external vac pump but that seems like a pointless effort when i could just go over the basics and fix what is wrong.

Specs
MS (I can post maps and settings just ask away)
Yoshifab block adater with DSM CAS and LS Coils
1994 B230F w/ H Beams but stock n/a piston.
530 head with big valves and springs from the GB.
Enem V16T cam set at +2
HY35CW

No vac leaks that i remember ( I will double check but NIW intake and no leaks which is not easy to fix on this manifold)

Car runs like a dog down low, takes forever to spool and just overall sucks off boost but once boost comes in full tilt a hoot @ 27psi. I do have some peak rpm issues but that is another problem (maybe)

So the big thing is what do I need to double check in MS and on the engine to make sure engine vac is what it should be. I seem to remember it being better as only the last few years i have had this brake issue (i only drive this thing maybe 1-2k miles a year so it is not the end of the world.

Thank you for the time.
 
Has your timing belt skipped at tooth?

If you have flood clear setup in MS, you could push the pedal all the way down and do a Tooth Logger log during cranking, or just listen to the cranking cadence, and make sure it's even. You can also do this without flood clear by disconnecting all the injectors.

Can you find some old logs and compare idle MAP then and now?
 
I haven't checked compression in ages. But I will put it on my list, honestly I do not think I have done it on this engine as it was a 195psi motor before I put rods in it and back in.

I will double check the timing, I have been wanting to replace all of my blue belts on all 4 redblocks here so maybe this is an excuse to take a weekend and knock them all out.

I did fix my bogging issue by looking at old tunes and logs and somehow my accel enrichment was way off the charts. So this gives me a day to go over some of the data points to see if my old logs show a date of healthy vac.

Now I just need the time to do all of this basic stuff. I will report back, thanks for the starting points as like I said just to fried to even focus on basics.
 
For what it’s worth, the 16 valve turbo with penta cams hovers around -10 vac at idle. N/a compression pistons with valve releafs cut but nothing fancy otherwise. Cadillac brembos up front with the stock volvo booster. Higher lift cam(s) will make less vac than an emissions cam.

What booster are you using? You shouldnt need an additional vac pump just for the brake system. All of the vacuum operated climate stuff works like it’s supposed to?
 
Your title says vacuum at idle is too low. Care to tell us what your warm vac at idle is?
If you meant you get 5 to 8 inches at warm IDLE, yeah you really need a milder cam if you really need vacuum for your brakes. Or change to non-vacuum assist brakes. Guessing you have 9-ish compression ratio? Could be worse. You could have 7.5 CR like my B21FT. I purposely use a B cam currently, because the Unitek turbo cam i WAS using (equivalent to iPd turbo cam) couldn't make enough vacuum. The B cam gives less power at higher revs, but it makes the low CR manageable.
 
For what it’s worth, the 16 valve turbo with penta cams hovers around -10 vac at idle. N/a compression pistons with valve releafs cut but nothing fancy otherwise. Cadillac brembos up front with the stock volvo booster. Higher lift cam(s) will make less vac than an emissions cam.

What booster are you using? You shouldnt need an additional vac pump just for the brake system. All of the vacuum operated climate stuff works like it’s supposed to?

Running the stockish 8.75" booster for the non ABS 744 (which is mine). I just changed boosters with the same results. The climate control stuff kind of works but that is normal leaks they have. While I do need to add a vac pump (Cruise control module) like i have on my other 3 cars I do not think this is enough to cause that much of any issue but I will test with it disconnected.

If you meant you get 5 to 8 inches at warm IDLE, yeah you really need a milder cam if you really need vacuum for your brakes. Or change to non-vacuum assist brakes. Guessing you have 9-ish compression ratio? Could be worse. You could have 7.5 CR like my B21FT. I purposely use a B cam currently, because the Unitek turbo cam i WAS using (equivalent to iPd turbo cam) couldn't make enough vacuum. The B cam gives less power at higher revs, but it makes the low CR manageable.

Yes around 5-6 in gear and 7-8 at idle. I do have this RSI stage 5 cam here still in a box that if it is still good then I guess I could swap that in and see how it does. My CR should be around 9.8:1 with the n/a pistons, this motor when it was pulled was a 195psi / cyl but i still have yet to check it with it in my car as it sat for 7+ years before it tore it down and put rods in it to install.

What might be my other options for non vacuum assist brakes?


Has your timing belt skipped at tooth?

If you have flood clear setup in MS, you could push the pedal all the way down and do a Tooth Logger log during cranking, or just listen to the cranking cadence, and make sure it's even. You can also do this without flood clear by disconnecting all the injectors.

Can you find some old logs and compare idle MAP then and now?

Ok so today I pulled the Nuke Cam gear and swapped on my new STS gear, double checked my Cam and CAS timing. With MS set for fixed timing at 10deg that is right about where #1 was flashing at so I am fairly certian that my trigger angle is set correct to match what is going on.

At the same time i did a smoke test and found zero leaks besides the normal throttle shaft tiny leak.

I am going to try to find some time today to look at some old logs to see if idle vac was any better. Looks like back in 2018 my idle was around 57-63 kpa and since 2019 it has been 67-75kpa. So i guess I need to figure out what changed during those years? I doubt the tune would do it but I will look at some old files and see if I can figure out via my picture albums what I might of done over those years.

Cranking sounds like all of the b230's I have here, while this car always sounded a bit beat i always figured it was the V16T cam causing the issue. Maybe it is time to retire the Enem stuff. Worse case I guess the newish head with valves might of been done incorrect and could be causing the issue, I guess a leak down test is in order.
 
Last edited:
Oct of 2019 I put on the big Valve head it looks like, I will double check data logs for that date range to see if that matches up with vac went downhill

IMG_20191111_071134.jpg
 
What might be my other options for non vacuum assist brakes?
I have three alternates detailed in my brake page.
Hydroboost and IBooster are both a bit bulky, but the third one is this compact electric setup that I think is pretty fascinating. It's remote and can be hidden behind a bumper, etc.

remoteboosterJEGSlo.jpg
 
I have three alternates detailed in my brake page.
Hydroboost and IBooster are both a bit bulky, but the third one is this compact electric setup that I think is pretty fascinating. It's remote and can be hidden behind a bumper, etc.
I found another option, Volvo used a vac pump in the FWD cars. Hella 009428087.

I still think something might be wrong but I guess this might be a fix that allows brakes to work.
 
I found another option, Volvo used a vac pump in the FWD cars. Hella 009428087.

I still think something might be wrong but I guess this might be a fix that allows brakes to work.
I just sent two brackets to be cut and bent to mount a Hella UP28 pump down between the driver side engine mount and starter.

My cam only pulls like 1 in Hg at idle. A quick mock up test with that pump was very promising for my brakes at idle. I got a pump from the junkyard from some newer Volvo. Once the brackets and hose get here I'll post some pics in my thread I'm sure.
 
What's your idle rpm speed?
+ 4 more degree to the camshaft and see where the vacuum level is.

Posting MSQ and MSL always helps troubleshoot.
 
I have the same cam and pull 18-21" at idle I think you need to check your timing belt and sprocket positions.
Really, I have never seen an IPD or V15/V16 cam pull more than 15. Plenty of times i have gone from 18+ down to 13-15 with just the cam swap.

Idle speed on mine now is 1000rpm, but anywhere from 800-1200 vac seems the same.



I think those are the same day files. That is just an idle log of it.
 
All your valves adjusted properly? My car with massive valves and a huge cam would do around 10-12inhg at idle in gear. When my valve adjustment was too tight it would idle with almost no vacuum at all.
 
Back
Top