Low HP readings

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My brother has a 2016 S550 with a V8 and a 6 speed manual. From the factory these are about 415 HP.
The car has a full performance exhaust, headers, sport cats and a cat back system. The intake is a Roush cold air kit, and it had a remap by Wortec.
On a rolling road it only made 428 HP, and put down 360 HP at the rear wheels.
This seems pretty poor as we were expecting about 470 HP at the flywheel, however the car feels way more than the figures suggest.
Do any of you guys have a similar set up with better HP numbers?

Regards John

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slowhand99 said:

How did the torque figures compare? That’s more likely what you can feel on the road.

The standard torque figure was 530 and increased to 541lb/ft so not a great increase.
The thing is the car feels very strong on the road and has instant pick up in any gear.
We might try another rolling road later in the year.

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CraigJ said:

Unless he had it dyno’d before the mods on the same dyno the results won’t mean anything as you have no base line. Every dyno will read different too.

Had he dyno’d it first it may have put out 400bhp for arguments sake then the mods would look good but he won’t know now.

I’d go for a 2018 intake manifold with MMR lock outs and a good tune from the likes of Lund or Palm beach dyno and see around or just over 500bhp combined with why he has already done.

Strange you should mention the intake manifold mod as he was talking about that the other day. I've told him to leave well alone as the car is fantastic to drive as it is.
I'm sure the Mustang would leave my Monaro in its dust in any case, but brothers never seem to listen do they!!!

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B3NNL said:

I had a dyno done after adding a cat back system, CAI and a canned tune. As yourself I was thinking start point of 415 so should be at least close to 440. We struggled to achieve 401 and that was only be returning the car to stock tune and keeping the CAI.
I then added ARH headers with sports cats and a 2018 Inlet manifold.
The car was then put on a Hub dyno up North and a bespoke tune carried out by Motorsport and Performance which resulted in 430WHP approx 495bhp.
I've since replaced the exhaust which was somewhat restrictive with a 3" Steeda cat back system and should be well over the magic 500 mark. Car drives amazingly and even gave the TVR boys a run for their money on our long weekend away last month which was a good marker as the car was standard last year and it never really troubled them, this year they all agreed that they couldn't pull away on me any more.

Thanks B3NNL,

Thats a very impressive result, I'll pass the info on.