Dip in torque 3500rpm

[Midnight]

Is it normal for the 172 to have a dip in torque around 3500rpm?

Not hugely noticeable on the road, I will be getting a AFR done soon so I can see exactly what is going on with the fuel mixture.

 

[Andyman]

Would like to know this too as a few of my old graphs have this dip and seen a few others on the RR thread have it, although many also don't.

 

[Chip-mk1]

Cam timing out is the normal reason its quite that bad.

 

[Midnight]

Cambelt has been changed around 600 miles ago, could that have anything to do with it?

 

[Chip-mk1]

Cambelt has been changed around 600 miles ago, could that have anything to do with it?

Yes if it wasnt timed up correctly that would be very likely to cause this sort of issue.

Who did it?

 

[Midnight]

Don't get me wrong the car goes extremely well on the road was just wondering if the 'dip' was normal.

Fred at BTM did the cambelt so I would have thought that's all correct, could the cause be anything else?

 

[Chip-mk1]

Don't get me wrong the car goes extremely well on the road was just wondering if the 'dip' was normal.

Fred at BTM did the cambelt so I would have thought that's all correct, could the cause be anything else?

I would be very surprised if Fred did it wrongly also.

As he is familiar with your car it would make sense to ask his opinion.

 

[Midnight]

I'll 'tag' him into the thread, hopefully he'll be able to shed some light on what he thinks could cause the dip.

Maybe a map / RS tuner would be beneficial but would rather diagnose the problem rather than covering it up so to speak.

Fred@BTM

 

[JamesWilson]

From memory my standard 172 had a dip around that rpm.

 

[Chip-mk1]

From memory my standard 172 had a dip around that rpm.

None of them have a flat torque curve, but that dip does look a little harsher than normal.

Although TBH it might just be due to the way they have scaled the axis looking again at the graph, it looks dramatic at a glance, but its only about 10lbft in fact.

So TBH, probably nothing to worry about.

 

[JamesWilson]

None of them have a flat torque curve, but that dip does look a little harsher than normal. Although TBH it might just be due to the way they have scaled the axis looking again at the graph, it looks dramatic at a glance, but its only about 10lbft in fact. So TBH, probably nothing to worry about.

Just had a check of mine, looks to drop 5-7 lbft before rising again, the scaling on the graph you posted is similar however the peak torque after is a lot more than mine.
Has the OP's engine got hotter cams by any chance?

For ref.

 

[Midnight]

I have no invoice of any camshafts, I was asked if it had 197 camshafts though?

Heard mixed reviews about the 197 camshaft in a 172 so have no idea...

 

[Fred@BTM]

looks fine to me, really bad scale! The power/torque curve should be crossing at 5252rpm, yours are at about 2250rpm by the look of it

 

[Midnight]

Like I say, it feels great on the road was just worried about the 'dip' but by the sound of it a lot do have a slight dip and if Chip/Fred is correct the scaling isn't great so looks worse than it is?

Can breath again now.

 

[JamesWilson]

Can breath again now.

Go take it for a proper drive and enjoy it!

 

[Adam G]

Just keep it above 3500rpm