Majorly down on power and running rich- Dyno chats to prove. What could be wrong?

Rob_94 said:

Hi there- Last week I took my car to a garage to have the 1st/2nd gear synchros fixed, new clutch put in, and value clearances checked and now I seem to be down on power by about 40hp. I thought I was going crazy but I took it to my local rolling road which confirmed this. I'm not going to name the garage as it could be a complete coincidence and something could have broken on the drive there or back (around 400 miles) but lets just say they are very reputable. I can't think of anything relating to the work done that could be causing this issue - however when I got home I realised the breather pipe from the rocker cover to the intake had not been reattached, so I wonder if anything else has been left disconnected or not attached properly.

I've ordered some new spark plugs just to check its not those, but I find it hard to believe they suddenly gave up the exact time I took it to have the work done..

One other thing I noticed is when in 5th at about 6k revs the engine starts juddering/ feels like the wheels are really unbalanced, but when I change up to 6th this stops completely

It seems to be running very rich at the top end - around 0.69 lambda

I really want to avoid driving all the way back to the garage if at all possible as my miles are already creeping up and I'd like to keep as much value on the car as possible.

Can you guys think of anything that could be causing this?

Cheers- Rob

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hollowaydc5 said:

Hi mate, mine was exactly the same. It was also running rich, and here's the dyno chart to prove. Mine was a clogged exhaust system. I'd disconnect the b pipe from the cat, it should totally change and pull normally. Unless you can unclog the system it'd be a new system.

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Rob_94 said:

They do look very similar- will definitely give it a try! thanks

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hollowaydc5 said:

You'll notice that as soon as the car comes into vtec there's a massive power dip, this is because the car can't exhaust the extra air due to the second cam profile and it's just blocked up. 100% your exhaust mate.

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Rob_94 said:

Sounds like an excuse for shiny new exhaust parts!

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hollowaydc5 said:

I bought a brand new Fujitsubo RM01A, fantastic exhaust and sounds amazing. I had a 5Zigen Pro Racer on which was causing my issue.

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Rob_94 said:

I also have a 5zigen Pro Racer exhaust! As if there wasn't enough proof already.. That'll be going on ebay

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carl hammond said:

Wow this is the second report of a 5zigen Pro Racer exhaust in as many months so seems these are either poor quality (don't last long) or just poor out the box... Glad the others here were able to help and hope it gets sorted soon, a Solid fabs setup on here for sale at a good cheap price I have seen so well worth considering as they get great reviews.

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Don't forget a lot of these exhausts are over 10 years old now. The lesser quality ones won't last forever.

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More than 2nd fella

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Liamneale69 said:

Really? What did you do with yours?

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hollowaydc5 said:

Gave it to a mate who is going to cut it open and straight pipe it

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Rob_94 said:

Update on this- I bought a Fujitsubo RM01A exhaust to replace the 5Zigen and the difference is night and day. Power is solid throughout the band and there is no dip in power when the car comes into VTEC. I haven't got the money to dyno it again just yet but I'd say it's gained AT LEAST 20hp.

So happy. Respect to SamDC5 for pointing out the issue.

Moral of the story is don't use a 5zigen exhaust.

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