: Boost Compensator Adjustment?



doug720
12-16-2010, 07:14 PM
I have been playing with my boost compensator adjuster in an effort to get more boost sooner(lower rpm's). I've checked the aneroid for leaks, and it appears good. My question, as you adjust the screw in or out, which way lowers the rpm for boost? Is this a suttle adjustment? I've screwed it in and it seems better, but how far can you go? So far a little black smoke, but very little. I have also given about a 1/4 turn more fuel to.

On the altitude side, I have just a small hose going to a clean air source inside the cab. Is there any thing else on this aneroid to connect? Is there any adjustments?

Thanks

Doug

Dougal
12-16-2010, 11:05 PM
On mine winding the screw out reduces the effect of the boost compensator. I played around with mine a lot but eventually bench set it to start moving at 4psi. This was the best compromise for me.

bush65
12-17-2010, 01:33 AM
I think it was Erik who posted this manual page some time back
http://i600.photobucket.com/albums/tt84/bushie39/BoostCompensator-1.jpg

Note there are a few typos - there are 2 item 19's (the control rack and diaphragm) in the diagram. The list below the diagram has the control rack as 18, but in the the description above both control rack and diaphragm are both 19. The full load screw is 18 in the diagram but is left out of the list below and description above.

Edit: my IP doesn't have a boost compensator or aneroid so I have no experience. I assume you adjust item 21 through a slot in the boost compensator housing.

doug720
12-17-2010, 07:24 PM
Thanks guy's for the advice. I read my FSM, but was not sure which way did what. I have been slowly working the adjustment inward, and performance is improving a little. I have minimal blake smoke. I was now think of trying a little fuel screw also? As long as the rpms are up, she pulls good, but a right turn in 3rd gear around town and it's a real dog until the turbo builds some boost. I can get about 12 lbs max boost. I have egt and boost gauges, what do you think about a little more fuel.

Thanks

Doug

Dougal
12-17-2010, 07:40 PM
Which turbo are you using again? The stock non wastegated turbo is matched for 3000rpm power and should be a dog down low (I own one but it's not fitted).

doug720
12-18-2010, 08:21 AM
Which turbo are you using again? The stock non wastegated turbo is matched for 3000rpm power and should be a dog down low (I own one but it's not fitted).

You hit on it, I have the stock non-wastegated turbo.

Will a stock 4BD2 waste gated turbo model bolt on (mounts+oil and water coneections)? I saw a brand new 4BD2 wastegated model for $400 US. I would like more/better low end power, is there a turbo you would recommend? I not looking for a racer, just better low end driveability with as much stock reliabilty and parts availabilty as possible.

Doug

nexxussian
12-18-2010, 09:01 AM
I haven't "adjusted" ;) either my boost compnsator, or the altitude compensator (aneroid).

Just what it says in my sig, plus about 1mm of timing advance.

The better I get the engine itself to run, the better I like the HY35W, but I still think the HE341 is a slightly better turbo for a single on these.

Dougal
12-18-2010, 01:27 PM
You hit on it, I have the stock non-wastegated turbo.

Will a stock 4BD2 waste gated turbo model bolt on (mounts+oil and water coneections)? I saw a brand new 4BD2 wastegated model for $400 US. I would like more/better low end power, is there a turbo you would recommend? I not looking for a racer, just better low end driveability with as much stock reliabilty and parts availabilty as possible.

Doug

The wastegated turbo has the same core and compressor side, so all those connections should fit fine, but I'm wondering if the distance from centreline of the turbo to the exhaust inlet flange is the same. It might be an optical illusion but the non wastegated turbos look to have a longer neck on them.
Honestly, I'd go holset. But I'd really like to find someone who uses them on a manual to compare low end response. Autos don't really use the low end torque.

doug720
12-20-2010, 09:28 AM
I'm going to adjust the boost compensator some more before a turbo change. It feels better the more I screw the adjuster inward. I wonder if maybe more fuel would also help?

Also, the altitude aneroid has a barb fitting on it. I have a hose going to a clean air source inside the cab. Is this correct? I could not find anything in the FSM on how it shpould be connected.

thanks,

Doug

astr
12-20-2010, 10:46 AM
...Also, the altitude aneroid has a barb fitting on it. I have a hose going to a clean air source inside the cab. Is this correct? I could not find anything in the FSM on how it shpould be connected.
Doug
If it is a 4BD2T, then the hose went to an electrically-controlled valve that was operated by the electronic box (QOS II). The other side of the valve went to a vacuum line. Under normal operation, the altitude compensator would be open to the atmosphere, as you have it now. When the QOS II determined that the engine was running too hot (water temp), it would switch in some vacuum to the altitude compensator making it think that the engine was at a higher altitude than it really was and therefore reducing the amount of fueling with the end result that the engine temps would hopefully go back down. A clever way to limit overheating!

Dougal
12-20-2010, 01:10 PM
How much altitude work do you do? If it's almost none then I'd disable the altitude compensator or remove it.

doug720
12-20-2010, 02:49 PM
We spend a fair amount of time at 7500' (2500m) and go up to around 11,000' (3650m) so I should keep it. I knew how the the stock set up worked for the alt aneroid, but wanted to make sure since all the stock temp/valve parts were removed.

There is an adjustment on the altitude aneroid, any ideas or suggestions on any adjustments on it?

On the fuel screw adjustments, any thoughts on adjusting it to give more fuel to help spin up the turbo earlier for better low end? Or is a new turbo in my future?

Doug

Dougal
12-20-2010, 03:25 PM
Yes more fuel will help spin the turbo up. But it will cause more smoke off boost and that part of the rev range may still be too hot EGT wise to use other than accelerating through.
I guess you'd need a sensitive vacuum gauge to adjust the altitude compensator. Make sure it's open at normal atmospheric and starts to close up after that.

Here's a useful altitude vs pressure table.
http://www.engineeringtoolbox.com/air-altitude-pressure-d_462.html