Dyno Enlightenment

[red17]

Ullo everyone,

Took my R32 onto the dyno today and came away with some interesting results. Firstly, it was stinking hot, intake temps were in the high 30's so i wasnt expecting much. It was more a test run to see how the car responds on a day like this.

I had run the car before in the current setup at registered 183hp at the wheels. However I was a little curious about the pressure difference between the dyno and my apexi boost guage. Dyno reads 11.5psi, boost guage reads 9.5 psi. Now the guage is tee'd off just below the point on the firewall where the dash one gets its information so I figured this to be a reliable spot. So either the guage is dodgy or the dyno is (im inclined to believe the 100 thousand dollars worth of precision machinery over my 300 dollar guage. )

So today i give it another go, i register a corrected figure of 180hp at the wheels on again, 11.5psi dyno reading (i dont run a bleed valve and my boost controller was off).

I then set the boost controller to high and ran 210hp at the wheels (corrected), guage reads 12psi, dyno reads 14psi. Now my car has a stock cooler, stock turbo but blitz management. After seeing the lambda graph we had grim looks on our faces. The blitz ECU is leaning out the mixture chronically when it comes on boost, causing it to miss and throw fuel out the back.

In fact even on the stock boost level run we could see the mixture leaning out on boost, but not at the level where detonation could occur. Still a concern.

Now theres 2 lessons here. 1. Don't believe boost guages, they can be out of whack by a fair way, to the point where theyre dangerous. 2. If you have a japanese aftermarket ECU map, throw it in the bin before you do some damage. Standard Nissan ECU's typically go full rich on boost, which ruins the tune somewhat but ensures no detonation or engine damage.

Im going back to a standard map and possibly buying an Apexi S-AFC so ive got some way of customising my fuelling, but safely.

Red17

PS: if the dyno is correct and the manifold pressure is at 14psi, does this mean the turbo is actually running about 16psi? Is the 14psi "safe" limit for ceramics measured before or after the cooler?

[Dr_Drift]

Red17: A lot of Jap ECU's are pluggin daughter boards or rom chips. These can be easily modified or removed without discarding the factory ECU, and save some money.

[slip]

how would a massive lean condition cause it to throw fuel out the back?

[Dr_Drift]

Slip - It can do wierd things when you start getting lean.... I wouldn't be suprised...

[red17]

When a cylinder misses, what happens to the fuel? Its gotta go somewhere, logically it comes out of the exhaust.

Dr Drift: already investigated the ECU issue, its just got a replacement rom on the board. Easy to take it out and put a new one in, or even just remap the same chip.

Ive since been told intake temps on the filter were at 45 degree's C. Im so sick of summer!

Red17

[rob77]

I love driving my car in winter on a cold dry night, its such a different beast. Intercooler should be here soon though which will help immensely I hope

[kjb_r33]

One thing you have to be careful of, an over rich mixture could be displayed as the engine running lean, oxygen sensors read the amount of oxygen in the exhaust, to rich and it wont burn, which means the oxygen wont either... The only way to know for sure is a 4 gas analyser, and look at hydrocarbons.....

[Steve]

when did you last do the plugs, I had a vast improvement just by upgrading my plugs - car stopped missing, idled better and vastly decreased detonation. Its the sort of thing that after I did it, whished I had done it ages ago - it might help.

[red17]

Fresh plugs, theyre about a month or so old.

Red17

[BOOSTMEISTER]

Is your fuel pump up to the task ? Mine wasn't and even at a touch over stock it would lean out at boost. I had a BLITZ ecu on my 32 and it was awesome and never had any problems ?

[JH32]

If you have the stock cooler, and you measure the 14psi at the plenum, wouldn't the turbo then be runnng somewhere in the vicinity of 19psi maybe 20?

I heard that there is something like a 6psi drop through a standard 33 cooler. I doubt that a stock 32 cooler would be any better?

[red17]

You may well be correct, i only used that as an example. Ive got no idea what the pressure drop actually is.

I may have found the problem with the boost guage too, but we'll see in the coming days.

Red17

[Guest INASNT]

Originally posted by JiMiH

If you have the stock cooler, and you measure the 14psi at the plenum, wouldn't the turbo then be runnng somewhere in the vicinity of 19psi maybe 20?  

I heard that there is something like a 6psi drop through a standard 33 cooler. I doubt that a stock 32 cooler would be any better?

yes especially on a hot day u get about 6 psi drop from 5000rpm and above witht the stock cooler!