[The Forbidden Supra]

Well, I did a few quick dyno pulls yesterday at 18-20 psi with my new T72 .81 Q-trim. I went there with a bunch of race fuel in my tank b/c I was planning on turning up the boost a lot more... but I didn't like the dyno or the people that worked there so I cut it short. My friend put his bpu supra on the dyno and all of a sudden it was popping and gurgling and didn't seem to run right, then I put my car on and it was doing the same thing. I have no idea what the deal was, but our cars weren't doing that on the way there. This was on a DynoPack chassis dyno, which I have never used/seen before. Two devices are used that bolt onto both rear wheel hubs. The owners claimed this type of dyno was much better than either dynojet or mustang dynos, and the numbers it reads are quite a bit lower than dynojet, but usually higher than a mustang dyno.

I think I tuned the timing fairly conservative and the a/f is very flat but quite rich, I think. The a/f meter at at the dyno was reading 12.5:1 and my brand new FJO was reading 11.8-12.0:1. They were arguing with me saying my FJO was a POS and theirs was 10x more accurate, but I thought they were full of crap, so I tuned according to my FJO. On the dyno, I remember my FJO reading about 12.1:1 which I thought was good and safe, but looking at the data I logged it's showing <1.6 volts from the o2 sensor... which was 11.5:1 or not even the last time I checked, so I really have no idea where my a/f is/was... somewhere between 11.5-12.5:1, and quite flat as you can tell by the graph. My fuel octane was about 105 octane, which consisted of 50% leaded gas and 50% unleaded. What a/f should be I tuning for with this fuel? 12.5:1? Or is that too lean? What about with a 50/50 mix of 93 unleaded and 110 leaded? (That's what I usually run)

Anyway, I dyno'd about 575 rwhp and 500 rwtq at 20 psi. I thought that was pretty decent but some people didn't. Want do you think? It looks to me like some cams would really help! The hp and torque especially fall off pretty fast. I didn't do a lot of tuning. I think I tuned the timing fairly conservative and the a/f was quite rich I believe. Please take a look at my timing map (if you know anything about timing that is) and tell me what you think. Specifically, I was wondering if it might be safe to increase the timing near redline, especially since the torque isn't very high there... my egt's were getting quite high after 6000 rpm, 1700 F by 7000 rpm. If you could help me optimize my timing and air/fuel for a 50/50 mix of 93/110 leaded and/or a 50/50 mix of 104 unleaded/110 leaded I'd really appreciate it. I also posted my knock data from the final run, which looked pretty much identical to every other run I did, so I don't think I really had any knock... maybe a tiny bit while the turbo was spooling. I'd like to tune the car for 22, 24, and 26 asap, but I want to make sure I'm on the right track before I do something stupid.

UPDATE: I totally forgot to mention, all of my dyno pulls were done at only 92% throttle. The guy dynoing my car didn't even press the pedal all the way down!! What happened is... I have this little button under the gas pedal that used to trip my nitrous when I had it... so you gotta push down just a tiny bit extra.. hardly more than the weight of your shoe. I really don't know how it's possible to not push the pedal down all the way. The guy dynoing my car must drive like a freakin' pussy. I just noticed that while looking over the data I logged...

-Paul

 

[The Forbidden Supra]

LOL, I'm a moron. I just realized why my torque and hp were falling off so fast. I had my knock table set too low from 6000 rpm on. It was retarding the timing 6 degrees from 6000-7000 everytime! No wonder the egts kept going so high at redline! Argh... what a waste. Maybe I'll dyno again next week... this time at WOT and with normal timing...

 

[OC]

Hi Paul!
Ahh...a clear explanation of the torque fall...I was like, damn, he REALLY needs cams! But even with the stock cams, it should not fall that much! I could not understand!! I guess that's what retarding 6 degrees does!! When you fix the timing issue, you should try to raise de redline to around 7200 rpm. Are you still on stock springs/retainers? The power looks alright for a 72 at 20 psi and a bad timing issue! There is a lot left in the tuning of the AF, as you don't seem to know where you are really standing right now. What were the numbers at 18 psi and conservative timing, i.e. street setup? The 264s will really come handy when you start turning up the boost!

-Olivier

 

[The Forbidden Supra]

Heh yeah. It's so hard not to make mistakes at the dyno. They charge so much that you sort of have to hurry, but then you do stupid things. I also had the timing restore rate set super slow, so if it knocked at say 2000 rpm it wouldn't restore it until about 15 seconds later lol. Well, at least I can be pretty sure it didn't detonate! The reason I only revved to 7000 is because it was getting so hot. Usually I rev to 7500 or 8000. My EGTs were hitting 1700 F b/c of the low timing and I didn't want to go any higher.

 

[The Forbidden Supra]

First of all, my EGT probe is in the exhaust housing of my turbo right next to my cast manifold, so it's quite close to the motor. Is 1700 F way too hot or is that ok for short periods? My EGT's like to go to 1650 F on a long pull normally. Is that a little higher than most people see? Should I increase my timing to get the temps down or is it 1650 ok? Thanks.

-Paul

 

[chnco]

Dynapack TQ numbers are usually REALLY low.

Did they use a tail sniffer as a A/F sensor?

 

[The Forbidden Supra]

Yep, they sure did! Whatever they used sucked. I can tell you that. I'm going to try a dynojet next time. I'll try the exact same settings first to see how the graphs compare. Actually maybe I'll try to go tomorrow or fri while I still have the same fuel in my car.

 

[SupraWood]

A/F will show a lean condition when read from the tailpipe. You are probably right where you need to be as far as those go. I am sure things will pick up with all the little problems you mentioned. I am really curious to see what numbers you produce. I have almost the exact same turbo (0.84 A/R turbine and water cooled are the only differences I can see). I am using an HKS manifold and have 264 cams, but haven't dyno tuned it yet. Good luck!!

Daniel