Rb20 Dyno Conflict

[AverageA31]

Gday all,

I live in semi-rural QLD, Ive had my rb20 cefiro dynoed twice, about 2 weeks apart, no difference to tune. Its running a remapped standard ecu and I wanted to check the AFR's.

The two dynos were different by 72 HP at the same boost, what the heck?

Im very confused as to how they can be so different.

Also the first dyno operator said my AFRs were unsafe and it was a "bad tune" so I decided to get a second opinion.

The second guy (lower reading dyno) however said AFR's were fine.

Who is right? Do I need a 3rd opinion?

RB20det

Mods:

Garrett GT2871R .48 trim/0.64 AR

GTR injectors

split dump into 3 inch exhaust

FMIC

Z32 AFM with pod filter

Remapped standard ecu for mods

Bosch 040 pump

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(1st Shop- tried 2 eproms, 1st was a little lean but headed for higher hp, 2nd tune got 246hp on14psi)

2nd shop- 174hp run was 14-15psi, 2nd run 188hp 17psi)

2nd Shop- AFR plotted at 17 psi

One last question, I have a power fc sitting around- is there likely to be any gain to me if I put it on and get it tuned?

I'd really like 300 rwhp,

thanks Jes

[JonnoHR31]

power fc would be better. those afr's on the full runs are fine, that half run is a touch lean but not enough to be dangerous.

the difference in power could be something silly like slightly different conditions sending the ecu into knock maps. did it feel different to drive?

[raZ1911]

You sure its remapped?

Power seems so low.

[Bsa]

Gtr injectors on stock ecu just wouldn't happen

[AverageA31]

Hey dudes,

thanks for the replies.

There was no difference between how the car drove either days-it felt fine both times so Im doubtful that it became a bag of crap for the second dyno shop.

Conditions ie temp were not very different either day also so I dont think that could do it, Im fairly certain it is a remap as I agree with the fella above that a standard (unmodified)ecu

cannot and will not run gtr injectors or z32 AFM to even a vaguely acceptable state without some tuning?

Does anyone have any revelations about how these two dynamometers could be so different? If the first reading of 246hp is correct can I still hope to reach my goal of 300rwhp?

If the second dyno is correct, I find it hard (and heartbreaking) that my car could be as slow with all the good bits as a nearly stock R32.

If I cant find any other solution Im considering driving to Brisbane if it means I get a dyno reading I can trust-then if the car is not up to scratch I can just say "lets try the power fc then."

Further background info if it helps.

Initially before either dyno printouts shown here the car ran a different motor, it was a bitsa RB20 made of 3 dead motors and it produced 170 hp on the mainline dyno shop(which supplied the second printout),

after this result I went home and did a compression test which produce 138-145 psi each cylinder but No. 5 which was 26 psi down (118? I think). Based on those results I though

I was starting behind the eight ball and went out and bought another rb20 with low kms and 160-165 psi per cyl. The seller gave me one of his old dyno sheets showing 165kw (with exhaust and pod).

I installed this new motor with all my bolt ons and then began my tale of two dynos.

Jes

[GTSBoy]

I must say, I find this fixation with the dyno numbers to be a bit vexing. Who cares what power-measuring-device-1 said and what power-measuring-device-2 said? How does the car feel to drive, and why do you have a target of 300rwhp anyway? Why is that number important? What would happen if you got that power reading from power-measuring-device-X and you weren't happy that the car was fast enough? What would happen if you got a 220rwhp reading from power-measuring-device-1and thought that the car was plenty fast?

[AverageA31]

gday GTS boy,

sorry to vex ya mate its ok. I dont have a mad love affair with numbers or anything.

The issue of 72hp difference on two dynos with same tune puzzles me, and a dyno is not accurate as a tuning tool whats the good of it?

Sorry to appear preoccupied with 300, Its a personal goal which I didnt think was unrealistic based on the testimonies of many others here and elsewhere.

I just want to go faster like everyone else.

Jes

[BLITZ-26]

dynos are only as good as the person running them

[The Mafia]

Dynos are all different.

You do a run before, make changes, and do another run and see what the difference is.

Most numbers are a load of horse shit, especially if you have a dodgy operator.

[DVS JEZ]

Exactly. Even strapping the car on different gives different results.