BBSC Boost Problems

C

coldhammer

Experienced Member
Joined
22 November 2004
Messages
631
Location
Atlanta
Hello all,

I have just recently purchased an nsx that has had the engine rebuilt with the 9.5 low compression JE pistons. The car also has the BBSC with the 6 lb boost pulley and an AEM unit. Additional Specs at bottom.

The work was done at MB's shop. I recieved the car but unfortunately ended up having to take it to a local shop to tune the AEM unit. The shop called me today saying that they have tuned the car and everything runs well except that the SC which is running a 6lb boost pulley is only putting out 3-4lbs of boost.

After talking to both the local shop and MB himself both have no explanation for the loss in boost. I was wondering if anyone on this forum might have any ideas or suggestions.

Please let me say one thing ahead of time. I am well aware of the rants and raves concerning MB and BBSC setup. Please refain from soapboxing.

BaschBoost Supercharger Kit (NOVI 1000 version) w/ 6lb boost pulley
550 cc injectors
AEM
Front and back Wideband O2 sensors
DC Sports exhaust
JE Forged Pistons 9.5 Compression Ratio with floating wrist pins.

Thanks in advance for any help.
 
Re: BBSC Boost Problemsq

How was the "3-4 lbs" of boost measured?
 
Re: BBSC Boost Problemsq

the obvious is belt slippage... check tension, maybe try gatorback belt to reduce slipping. then check for boost leak and patency of the vacuum line. what were the final dyno numbers? if you are in the expected range then it may make you question the boost numbers vs actual boost generated. BTW why 550's on 6 lb boost? seems like over kill
 
Re: BBSC Boost Problemsq

Hi guys,

The boost was checked both through the AEM and with a boost gauge. THe AEM measuerd 3 lbs and the guauge measured 4 lbs.

We checked the belt tension and there doesnt appear to be any slippage occuring.

The shop guy said he had not checked for leakage on the vacuum line. He is going to do that now and see if he finds anything.

THe dyno results came out at 260 WHP. Which is almost stock. THe shop tech said he "thinks" the low numbers are a result of running the low compression motor with low boost. Says that would just about bring it back to stock compression which would acocunt for the near stock hp.

As far as the 550's go, I went with the bigger injectors because the car was supposed to be running 10lbs of boost. However there have been a number of issues and the ten lb pulley was unavailable at the time. So the car was sent back to me with the 6lb on with the intent of upgrading to the 10lb once the pulley was fabricated.
 
Re: BBSC Boost Problemsq

coldhammer said:
We checked the belt tension and there doesnt appear to be any slippage occuring.

The shop guy said he had not checked for leakage on the vacuum line. He is going to do that now and see if he finds anything.
Click to expand...

I didn't think I had any slipping, either, but after changing to a Gatorback belt, I gained almost 1.5lbs of boost. The Gatorback belt number is 4060672 / 6PK1705 ; I'm not sure if the last number is the 6-pack number - in any case, I got it from a local AutoZone. Worth a try for $20 or whatever it is, and it's a lot easier on the BBSC shaft bearings.

The other easy trick is to make a mix of dishsoap and water, and pour it over the parts that may leak (fittings between major parts, etc). Fire it up and see if you get any bubbles. If so, you're leaking boost.
 
Re: BBSC Boost Problemsq

Mojo hit it right on the head, it is going to be either vacuum, or belt slippage, check the pipe between the Novi and the throttle body, and also the housing on the back of the supercharger, because if you adjust the angle of the supercharger and you dont tighten the bolts on the back correctly you may leak from the back...and if you lower the compression on any FI motor, you will have to increase the boost that much more to achieve the same HP numbers, you will have to increase your boost to show any improvement on you new low compression engine...Good luck to you on your endeavors

The King
:cool:
 
Re: BBSC Boost Problemsq

I was just thinking, if you brought the engine up on TDC #1 compression and marked the S/C belt and pulley (finger nail polish works well) you should be able to see any belt slippage using a timing light with an adjustable dwell (to compensate for timing adv) while at boost on the dyno. Never tried it, but it might work?
 
Mark, I think ths has been tried before, but without success. Trying to find the thread...

[Edit] Found a post by Andy regrading this.
 
Please let me say one thing ahead of time. I am well aware of the rants and raves concerning MB and BBSC setup. Please refain from soapboxing.

Agree 100%. I will bitch-slap anyone that tries to undermine this thread. Turbo NSX, are you listening?
 
the obvious is belt slippage... check tension, maybe try gatorback belt to reduce slipping.

You will be (at least I was) how much a little extra belt tension will restore boost on a SC'ed NSX. Along these lines, I run only the GatorBack belts.

BTW why 550's on 6 lb boost? seems like over kill

Definite overkill.....I run 500's with 11-12 PSI, resulting in a nice air-fuel ratio.
 
I was just thinking, if you brought the engine up on TDC #1 compression and marked the S/C belt and pulley (finger nail polish works well) you should be able to see any belt slippage using a timing

This will not work. I tried it and after scratching my head for a while, I realized why not. The “TDC” trick applies only to the crankshaft pulley, not the SC pulley. Unless the ratios of these two pulleys match, the “marks” will never align themselves. I have tried this idea…..a good one, but unfortunately it does not work out too well.
 
i don't think i can add much in the help department.. the previously mentioned troubleshooting tricks would seem to cover all bases. i do wish i'd also purchased a built motor when i bought my car however... my 7 psi bbsc is freaking awesome above 3-4k, i can only wonder what it would be like if i could safely run 12 psi...

Where are you located? perhaps if you are close enough to someone very familiar wiht the bbsc hardware, they can check it out for you?

oh ps, i believe andy vecsey once mentioned to me it took him 4 days of searching to find a lone boost leak, with him at his virtual wits end.. and it would seem andy knows his stuff about the bbsc, so i can imagine if i tried to find that same leak...

presuming the pulley is the correct size, that novi fan HAS to be spinning at the right speed, and therefore you MUST have a loose belt or boost leak somewhere..?
 
AndyVecsey said:
I was just thinking, if you brought the engine up on TDC #1 compression and marked the S/C belt and pulley (finger nail polish works well) you should be able to see any belt slippage using a timing

This will not work. I tried it and after scratching my head for a while, I realized why not. The “TDC” trick applies only to the crankshaft pulley, not the SC pulley. Unless the ratios of these two pulleys match, the “marks” will never align themselves. I have tried this idea…..a good one, but unfortunately it does not work out too well.
Click to expand...

I thought about that, but you would think that the relationship between the crank at TDC #1 and the S/C pulley would be constant assuming the belt isn't slipping (as if it was geared). The actual firing of the #1 cylinder (strobe light) will occur only once for every 4 (+/- 1/2) rotations of the S/Cer pulley depending on your actual ratio, but the relationship should stay relatively the same. I think the problem is that normal timing advance will skew the relationship, That's why you'd need to adjust the dwell and null it out. If the two marks don't drift too far apart, you're golden anyway since we're looking for a major shift (ie; slip). Maybe TWO timing lights, one focused on the belt mark and one focused on the pulley mark would take all the "bias" out and all you look for is the relative movement of the marks.
 
Even if you could mark the belt, you likely will not see any slipping until in boost conditions, anyway.

An occasional slight belt chirp at start-up is a sign of a loose belt... but unfortunately not a reliable indicator. Like others have said, it really HAS to be the belt. I'd advise to remove the belt and thoroughly clean the pulleys - especially the crank pulley as you may have gotten some oil or other contaminate on it. In this scenario, you're going to see a belt slip (no/low boost) almost regardless of tension.
 
Well we spent a good while yesterday going over everything trying to find a boost leak. No success on that front. I am going to go ahead and try putting on a gatorback belt today and see what the results for that are. Ill keep you posted.

Thanks for all the feed back guys. I appreciate it.
 
If the belt isn't the solution, try blocking off BOTH ends of the bypass valve tube. The valve may be open slightly allowing boost to cycle back to the vaccum side of the throttle body.
 
So the Boost problem has been solved. It turns out that the tbolt connecting the intake to the blower housing was just loose enough that at aroudn 3-4 lbs of boost it would start to leak.

This was determined completely accidently. After upgrading to the 8 lbs pulley and still not getting an increase in boost the guys at the shop just started going back and tightening everything on the SC down. Turns out when he got to the Tbolt it moved just a hair. Funny how the slightest thing could cause such a problem.

So now the car is running 8 lbs of boost successfully. But alas there seems to be a new problem. Well this isnt actually a new problem so much as revisiting one of the original problems.

It seems im getting a lot of random variations in driveablity between drives. Keep in mind that the car is now running an AEM unit.

For instance during one drive the car will stutter noticibly at low throttle, like its not getting enough fuel or something to that effect.

Then the next time i drive the car the stuttering is "almost" completely gone but when sitting still the idle fluctuates widly, sometimes to the point of stalling out.

Sometimes the oil pressure gauge reads 4 at 3k rpm cruising. While other times it reads as low as 2 or as high as 6.

The problems are not consistent and seem to change between each running of the car. From a programmers standpoint it seems almost as if the data in the AEM is getitng corrupted randomly.

Any ideas?

Also if anyone knows ZRO260B4U could you have him try and get in touch with me as I know he was running a similar setup and is also located in atlanta. For that matter i would be interested in talking to anyone in the atlanta area.

Thanks again for the help.
 
It is very likely that the stuttering and idle problems are tuning related (not hardware related). I would also check spark plugs as well - another member on this board traced several issues he was having back to fouled plugs. A good set of colder heat range plugs will do a lot of good regardless.
 
PaynNSX said:
A good set of colder heat range plugs will do a lot of good regardless.
Click to expand...

Devin, before you disappear into the wilds of the East, will you be updating your email to reflect your new status and enshrinement? We here in the West would hate to lose your expertise to those Yankee types forever.

(You will still be driving your NSX there, right? And still talking to us? Not cabbing it like those crowded metropolitan folks do?)

And -- oh yes... good luck and congratulations! (Soto voce: ) Dammit!....
 
PaynNSX said:
I would have to say look into the tuning a little bit more.

Who is doing the tuning?
Click to expand...

I concur.
crimson.jpg



Armando
 
Tuning is being done by Doug Wilks at Top Speed in Atlanta. He comes refered by AEM as one of the top AEM tuners in the south east.

Im going to drop the car back off at the end of this week and he will drive it around for a few days as a daily driver to see if he can figure out whats going on.

Because of the randomness he is not seeing a lot of the issues I described here during a short test run.
 

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