Lost 20 whp with new exhaust and flex fuel kit

[the_wilferine]

I had my car on the dyno again on Saturday after fitting a Milltek cat back exhaust with OPF bypass and the BM3 Flex Fuel kit, running CustomROM stage 2 MultiMap v1.1 and for some reason the power is down a little over 20 whp. It’s the same dyno as the previous run in May, same fuel type (Shell V-power), I was planning on doing a run with ethanol but there didn’t seem much point given the unexpected lower performance on pump fuel.

We’re not sure what’s going on here and the little spike towards the high end of the rev range seems weird.

Unfortunately I didn’t get a data log from the previous run but I did this time: https://bootmod3.net/log?id=654f5ce8a23143319ce76eb0

Other performance mods, which were fitted prior to the previous run:

• Armaspeed carbon intake
• Forge Motorsport chargepipe
• 200 cell downpipe

I’m really curious to know what’s going on here and would massively appreciate it if anyone can interpret the datalogs and help get to the bottom of it.

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[Thraxbert]

What was the temperature, DA, and IAT for each dyno session?

 

[the_wilferine]

What was the temperature, DA, and IAT for each dyno session?

I don’t know for the run before this one (365whp), I only have datalogs from the latest session where it made 343whp and they’ll be in the linked logs.

 

[Thraxbert]

If my reading is correct:

OEM exhaust is 70-81mm
OEM GPF section is 81mm
Your new exhaust is 70mm all through

I strongly suspect your performance loss is because you actually sized down on the exhaust, which is especially negative on a turbocharged vehicle. The loss of modest 8 wheel torque is symptomatic of exhaust restrictions.

 

[D3ad_Hand]

If my reading is correct:

OEM exhaust is 70-81mm
OEM GPF section is 81mm
Your new exhaust is 70mm all through

I strongly suspect your performance loss is because you actually sized down on the exhaust, which is especially negative on a turbocharged vehicle. The loss of modest 8 wheel torque is symptomatic of exhaust restrictions.

I agree with Thraxbert here.

OP why go with 70mm exhaust? Better to have something going from 3.5 to 3.0 dual pipes or 3.5 over the whole exhaust.

 

[razorlab]

There is timing pull of 3-4* starting at 4,700 rpm, which is exactly where your power drops on the dyno chart.

Did you only do 1 pull?

 

[the_wilferine]

If my reading is correct:

OEM exhaust is 70-81mm
OEM GPF section is 81mm
Your new exhaust is 70mm all through

I strongly suspect your performance loss is because you actually sized down on the exhaust, which is especially negative on a turbocharged vehicle. The loss of modest 8 wheel torque is symptomatic of exhaust restrictions.

The OPF bypass is 80mm according to the site I bought it from https://milltekshop.com/gpf-opf-byp...-uk-european-with-opf-gpf-2019-2020-ssxty116/

Where are you seeing that it’s 70?

The rest of the exhaust is 70mm. The OPF bypass converts the single pipe into dual pipes.

I guess the pipes could be smaller overall but I’d have expected the lack of OPF restrictions to have at compensated for that.

 

[KBGT]

4th gear dyno run and timing corrections where power drops off???

 

[the_wilferine]

There is timing pull of 3-4* starting at 4,700 rpm, which is exactly where your power drops on the dyno chart.

Did you only do 1 pull?

Interesting, no we did 4 runs overall, at first I thought it might have been the new v1.2 of the BM3 MultiMap released in October so went back to v1.1 but that made no difference.

 

[razorlab]

Interesting, no we did 4 runs overall, at first I thought it might have been the new v1.2 of the BM3 MultiMap released in October so went back to v1.1 but that made no difference.

Temps the same as before? Were you in Sport mode?

Do you have datalogs of the other 3 pulls?

 

[zrk]

With out logs we can't really tell you much.

 

[the_wilferine]

Temps the same as before? Were you in Sport mode?

Do you have datalogs of the other 3 pulls?

I don’t have data for the previous session where it was making 365whp but it was in May so would most likely have been warmer.

The only other log I can find from Saturday is here: https://bootmod3.net/log?id=654f5cb767522b0918a9c6c2

 

[the_wilferine]

With out logs we can't really tell you much.

I linked the logs in my original post

 

[razorlab]

I don’t have data for the previous session where it was making 365whp but it was in May so would most likely have been warmer.

The only other log I can find from Saturday is here: https://bootmod3.net/log?id=654f5cb767522b0918a9c6c2

Still timing pull. You are also about 3-5psi off boost target but some of that could be from the cooler weather.

 

[Axix23]

For a dynojet, those are some incredibly low numbers…….

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