another 1/4 run with ther M90+nitrous

[SuperRunner]

So I ran a 14.88 @93.6 with no nitrous. My best boost only pass.

I then slowly upped the nitrous shot until I got to a 75 shot.

[email protected].



Unfortunatly my tires are bald so I couldn't hit the nitrous until just after the 2nd gear shift, or I could have shaved off another .2 seconds easy and got down into the 13's. Oh well.

At sea level this will be a low 13 second car, and possibly in the 12's with some good tires to take the nitrous hit off the line.

BTW, the fuel system is still COMPLETELY STOCK!!! I did hear a little detonation up top, but rather mild. I should have made a run with my ECT power button turned off to pull out a little timing. Again, oh well

 

[4000GT]

If the det is audible sitting in your car doing a high speed run, its causing pretty decent damage I would expect. When you can hear it, its never little... (guessing you had head protection on as well?). 12's are a long way from 14's... I would have expected a higher trap speed given the power you are putting down?

Must be good to get out there and post a time anyways!

 

[SuperRunner]

14.0 to a 12.9 isn't that far when the 14.0 is at 4600 feet. Take that down to sea level and run some drag radials so I can run nitrous from the dig, 12.9 should easily be obtainable. Trap speed should definatly be much higher but again, I am a 4600 feet with a positive displacement charger. Elevation kills them.

As for the knocking, at 7psi BARELY audible detonation isn't to much to worry about. Now at 14psi, I would worry. At 7psi pressures just really aren't high enough.

 

[ed_ma61]

detonation is detonation. its about the volatility of the mixture, wtf does 7psi vs 14psi mean if its pinging?? your engine mate, but yeah, thats well bad...

 

[SuperRunner]

Becaue at higher psi, the combustion pressures are MUCH higher. At a lousy 7psi the pressures aren't high enough to cause any damage.

It is like saying detonation by running 85 octane gas in an old beater truck pulling a hill in a low gear(I HEAR this quite often) is no different then detonation in a 30psi race motor.

The old truck will run for 20 years doing that, the race motor will last for 1 milisecond.

PSI has MUCH to do with how damaging detonation can be.

Believe me, I know what damaging detonation sounds like, and this was no where NEAR that, and also no where near what I put my 750rwhp supra though while tuning. I tune VERY close to the edge, and have never blown a motor....yet(cross fingers)

 

[SuperRunner]

pulled all the plugs. No signs of detonation.

Like I said, it was barely there, and it would instantly clear up when the ECU pulled timing. Most people probably wouldn't have even heard it.

 

[4000GT]

Why does your ECU not pull timing before you are hear det? What ECU are you using?

Weird that you heard the det up top too... I thought det was comparatively less in high rpm because of the reduced peak cylinder pressures.

By the way you are talking about boost pressure you would think an NA motor would never det if 7psi isnt enough to cause damage!

Anyways, good luck out there with the next race.

 

[spf_lexus]

Im running 7psi also but procharger. I ha no idea the ECT altered timing, I assumed it was JUST tranny/shift points but thats explains why i rather drive it with it off rather than on. Engine is less spurratic, performs as needed and is "calm". Anyone know that exact changes?

I know this is a noob question but here i go. Whats detonation sound like? I assume im running a little rich from the buildup in my tail pipe but dont know for sure and would like an idea to look out for in the future. 7psi intercooled 300-310rwhp using RRFMU.

 

[4000GT]

Det sounds like popcorn popping... too rich and you get bore wash...

 

[ed_ma61]

imagine shaking a large tin can with a handful of dry rice in it

 

[SuperRunner]

Stock ECU. And not always can the ecu pull timing before you can hear audible detonation. That is why it would come and go so quickly. Also it proabably had to do something with the long shift time, and the amount of nitrous. Might also have something to do with my plugs. I am running 7's when I should be running 6's.

SPF_lexus, it isn't the 7psi that caused the tiny bit of detonation. It was the fact that I was running a 75 shot along, on stock fuel, stock ecu, stock fuel pump and even stock fuel pressure.

Most people get an FMU for just 6psi non-intercooled. Just goes to show that an FMU is probably not required on an M90.

The ECT generally advances timing through the entire RPM range. I found that out when tuning a truck awhile ago with a supra motor in it. I got the O/D and the ECT wires backwards after I had tuned it with a good amount of base timing. Then I took it out on the highway hit the O/D button and got MAJOR detonation. The rattle can type, not the sparatic type I was getting in my lexus.

At any rate, I have enough tuning experience to know how bad detonation can be, and I didn't feel like this was an issue.

On the way home, on the highway, I did a few long pulls, then I remembered the ECT. So I turned it off and the LITTLE detonation I had went away. It felt to pull a little harder as well.

My point of bringing up the detonation bit was just to show what the BONE STOCK boosted car can do. I will hook up my widband on Monday to see what my AFR's are.

 

[kc95sc400]

So, I'm curious, what are your intake temps like.

I've been beating the heck out of my engine with 10ish psi for awhile now and I've only ever heard detonation twice. Once was on the street and was likely my fault. I punched the gas, changed my mind and let off, then changed my mind (again) and punched it again.

The only other time was during two runs on an 1/8 mile track without my intercooler installed. Seemed to start pinging about the same moment my intake temps reached 195 degrees.

My ECT button is ALWAYS on by the way.

I'm asking because I've been considering a 50 shot. I haven't looked into it too much cause I don't want to blow the motor.

KC

 

[SuperRunner]

running the 50 shot you might want to keep the ECT button turned off. You always want to retard ignition when you use nitrous.

50 shot is still pretty small and you shouldn't have a problem. Remember, it will cool your charger further. Temps won't be a problem especially if you are intercooled.

I have no idea what my intake temps are, but I know the water/air setup is working great. Before the intercooler you will burn your hand if you touch the plenum. Then on the intercooler itself and after, you can hold your hand on the plenum. It will be quite warm, but it won't burn you.

 

[jibbby]

Super - I have ran 100 shot for years on the stock Lexus/Soarer ECU and piggyback unit to enrichen the fuel mix some.....No retard of timing was needed...Went to a 150 shot the pinging started at high rpms at times....

That's my experience with nitrous shots on the 1uzfe....

 

[SuperRunner]

I have nothing to enrich the mixture. That would be the main differnce, I may be a little lean. Plus like I said, my ECT was turned on. I turned it off an all detonation went away.

What type of FI were you running at the time, and was int intercooled?

Where did you inject?

So you say that up to 150 shot with a piggy back would be ok on a single port wet shot?

 

[stevechumo]

I've been running 9 psi without any pinging yet. I have the FMU and the 255 LPH-HP fuel pump. I have the ECT on all the time and I find the car is a lot faster with it. If I have it off, the car will be very slow at around 50 mph and when under boost, I don't have enough time to turn it on.