Johnyquest

Hey fellow HT-ers...

I've had my setup for about 6 months, as follows:

stock d16z6, drag mani, volvo 740-t3, afc hack, homemade downpipe, homade/modified fmic, homemade chargepipes, tial 38mm wastegate, homemade dumptube, stock timing, etc.

7-11psi, depnding on my mood, via homemade boost controller.

Now the question...
Do you guys boost part throttle with the afc hack, and do any of you hear detonation? I've been super paranoid about part throttle boost ever since I put my setup together, and though the computer does manage to hold the a/f ratio around stoich when in closed loop, stoich is too lean for safe boosting, correct?

So, how much boost do YOU guys run, and do you feel safe boosting at part throttle with the hack??
If yes, have you done anything to take any precautions? If no, then your in my boat.

Looking forward to your feedback!

Bailhatch

I run a really small nissan t3 like yours (you shoulda got the 760 turbo w/ the bigger exhaust housing) at 8.5 psi with 1.5 degrees pulled out. I boost part throttle all the time. no problems except a little hesitation at very very low throttle bit it is definatly not hurting the engine. I also run it pretty rich, like -32 till 4k then -30 to 8k. smells great. I'm changing my plugs 2 ranges colder soon. That can help prevent detonation too.

Joseph Davis

You're going to be just as well off WOT as you are part throttle.

Honda ECUs stick themselves in open loop whenever the TPS increases, the MAP pressure increases, or the RPMs increase at a certain rate. Due to a small .48 AR turbine on my LS, I can boost at 25% throttle on the highway... from 3500 rpms to 7000 redline the ECU stays in open loop.

Your ignition timing for an AFC hacked Honda is no worse under part throttle boost than WOT throttle boost if it's the same boost level. I don't care for the excess advance at transition to boost and low boost, and chip my ECU to correct that.

Johnyquest

I didn't know the 760's had a better exhaust housing... to be honest, i'm not sure wheather my turbo is a 740 turbo for sure, anyways. The kid I bought it from didn't know, and I saw a picture of one on a website with the same weird flange as mine (the round countersunk deal) and discovered that I had a volvo turbo. The picture looked like mine, and was a 740, so I assumed it's what I had.... all off topic....

so you've only pulled out 1.5 degress and never heard a hint of detonation? I'll go outside and play soon, toward the firewall is retarding the timing, right?

And how are you running with only -32 pulled out? no CEL? maybe b/c you are running such low boost.

Thanks for the responses everyone.... and J Davis: what are you using to chip your ECU's? Anything for a p28?

Joseph Davis

Volvo 2.8 turbo (760) got .63 AR turbine, 2.1 turbo got .48 AR. Same compressor. I wouldn't call one that much bigger than the other, but the turbine helps with top end ESPECIALLY when/if you get a big fat compressor that flows a lot more than the Volvo piece.

For OBD0 you should run Ghettodyne boost code. For OBD1 you should run Uberdata boost code. I just run a chipped AFC hack for the same reason I ran PVC charge pipe - everyone looks at you like your crazy, can't believe you're faster than they are, and has an opinion why you should do things otherwise. If you haven't noticed, I'm not right in the head.

Bailhatch

Ya, it's really fun building stuff for pure function and value. I built my whole turbo setup and engine swap for under a grand. People hate me because I am so budget and so fast. My coilovers are worth more than the car . The guys with $30k cars at auto-x don't seem too happy either. If i knew as much as this J Davis fellow i could really **** off the rednecks and ricers around here.

Um i think turning the dist clockwise (top tword radiator) is retarding or maybe i'm retarted.

Johnyquest

I actually thought retarding your timing was towards the firewall, so hopefully someone can clear that up.

I just had an idea to help us out with closed loop boost. I don't know if it's a stroke of genius, or a bout of stupidity, but here goes:
Since the ECU tries to keep the a/f ratio hovering around stoich, by referencing the voltage of the 02 sensor, couldn't we slightly modify the voltage that is returned to the ecu by the sensor via some simple circuit, to fool the computer into thinking it is leaner than it is, therefore slightly richening the part throttle a/f ratio and allowing for safe(er) part throttle, closed loop boosting?

IE, if the o2 sensor goes 0-1v, and .5v is stoich (guessing?), then the computer obviously tries to keep the a/f ratio hovering around .5v. If we could slightly modify the sensors output, ie return, for instance, linerarly, a value that is slightly less than the actual value, i.e. .4v when the sensor outputs .5, and .3 when the sensor outputs .4, etc, the ecu would be fooled into richening the a/f ratio in a controlled manner, and would allow us to run more boost part throttle, more safely.

Now, I could have just made all this up and it can be all stupidity, and it may be worthless, but it really seems to me like it could help out. It would probably (most definatley) result in a slight decrease in gas mileage, but it may be worth it for the safety of our engines?

Anybody who reads all that, tell me what you think.