Jerking before vtec

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g_mac

Active Member
Messages
99
alright folks

just got the car back from having the map tweeked and it stil didnt sort the problem out. just before vtec comes in around 5500-6000 there is a dip in the power curve but a more noticable dip in the torque curve, (although i know this is a common problem it was never as bad before i did the engine work)! if u dont change gears quick enough then it drops into this part of the rev range and the dip would near put you through the windscreen!
cant scan the graph in but the torque curve drops from about 155 @5500rpm to 137 @5900rpm and the power curve drops from 165 @5500rpm to 154 @ 5900rpm! the mapper did his best but could only narrow the problem down to either exhaust cam timing or the manifold!
has any1 heard of a dc sports manifold restricting the car (bare in mind my car is running 270 + bhp) as he thinks it is no good after 250 bhp and the Toda would be the better manifold?

any1 else shed some light on this situation?

car has
Toda A3 cams,
Toda valve springs,
Toda Head gasket
Toda Chain Tensioner
Head Work
J's Racing 70mm Throttle Body
RBC Inlet
Gruppe M
DC Sports Manifold
RM01 Cat back system
...

Thanks

PS my car also doesnt make peak power until 8800rpm, scary rev'n it so hard :shock:
 
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ally_mac

Advanced Member
Messages
353
It was first mapped by a fella called Steven Gault, he does a lot of work with rallycross and hill climb cars and has worked on a lot of honda engines, included honda powered minis. It was taken to a second mapper for a 2nd opinion, this mapper works a lot with Autronics, ECUtek, has also unichipped quite a few k20 engines and has mapped 3 hondata so far and he could only improve the map slightly. I personally think its nothing to do with the map, especially as 2 very good mappers have been unable to sort it so it is not down to ilimateing parts on the car which can turn out to be very expensive

P.S. We are from N. Ireland which is very it wasnt taken to the likes of TDI, but we have spoken to them on the phone a few times and they are baffled by it also
 
MilanoChris

MilanoChris

Advanced Member
Messages
5,649
ally_mac said:
It was first mapped by a fella called Steven Gault, he does a lot of work with rallycross and hill climb cars and has worked on a lot of honda engines, included honda powered minis. It was taken to a second mapper for a 2nd opinion, this mapper works a lot with Autronics, ECUtek, has also unichipped quite a few k20 engines and has mapped 3 hondata so far and he could only improve the map slightly. I personally think its nothing to do with the map, especially as 2 very good mappers have been unable to sort it so it is not down to ilimateing parts on the car which can turn out to be very expensive

P.S. We are from N. Ireland which is very it wasnt taken to the likes of TDI, but we have spoken to them on the phone a few times and they are baffled by it also
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Run a datalog on the car mate, 4th gear from low revs to limiter and send it to milanochirs@hotmail.co.uk and I'll have a look at it for you.

The DC mani, while not as good as the Toda, isn't the cause of this jerkyness IMO, if it's making power high up in the rev range then there's no reason for a stutter.
 
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ollie-dc5

Advanced Member
Messages
416
I think this is all to do with cam angle as the vtec comes in. My vtec was set to 3500 rpm and I had this huge dip in power. I took it to TGM yesterday and got Romain to have a look at it and he adjusted the cam angle and changed the vtec crossover point to 3700 rpm. This has now sorted it. HTH.
 
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ally_mac

Advanced Member
Messages
353
MilanoChris said:
Run a datalog on the car mate, 4th gear from low revs to limiter and send it to milanochirs@hotmail.co.uk and I'll have a look at it for you.

The DC mani, while not as good as the Toda, isn't the cause of this jerkyness IMO, if it's making power high up in the rev range then there's no reason for a stutter.
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Havent played with the Hondata software much mate, so how do you run a datalog and i will send it to you for a noisy

ollie-dc5 said:
I think this is all to do with cam angle as the vtec comes in. My vtec was set to 3500 rpm and I had this huge dip in power. I took it to TGM yesterday and got Romain to have a look at it and he adjusted the cam angle and changed the vtec crossover point to 3700 rpm. This has now sorted it. HTH.
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Thats what we though but the 2nd mapper tried a couple of different cam angles and it didnt help it at all. The only thing I can think of is the exhaust cam angle is not variable so if its not set to the correct angle it could cause the car to lose power, but as we arent using adjustable pulleys, your cam angle is either going to be right or wrong and if its wrong you wouldnt even be making good power. Unless we need adjustable pulleys to fine tune the exh cam
 
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fonz600

Advanced Member
Messages
575
Send me a copy of your datalog and map as well mate.
I'll take a look at it for you.

How come 2 different posters are talking bout the same car? Are you the same person?
 
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g_mac

Active Member
Messages
99
i thought it wasnt the map and it had to be something else as 2 very good mappers have had a look at it! how do you do a datalog MilanoChris an i will do 1 2nite and email it?
yea there's 2different posters, ally_mac is my bro and used to own the car, i own it now! 8)
 
MilanoChris

MilanoChris

Advanced Member
Messages
5,649
You need to connect a laptop to the ECU with the engine running and set K Manager to record the datalog. Not done it for about a year so not 100% sure on exactly what it is you do/press but it's straight forward.

Ask yourself this if you are confident in the mappers. Why will the car rev freely and make 270bhp yet it's jerking when just before VTEC engages? I bet if you was to fit a standard ECU then this wouldn't be the case. There's an issue with ignition timing//fueling/cam angles.
 
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g_mac

Active Member
Messages
99
MilanoChris said:
You need to connect a laptop to the ECU with the engine running and set K Manager to record the datalog. Not done it for about a year so not 100% sure on exactly what it is you do/press but it's straight forward.

Ask yourself this if you are confident in the mappers. Why will the car rev freely and make 270bhp yet it's jerking when just before VTEC engages? I bet if you was to fit a standard ECU then this wouldn't be the case. There's an issue with ignition timing//fueling/cam angles.
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ok will have a try later on 2nite or 2moro and see if we can get a data log for u's to have a look at
 
MilanoChris

MilanoChris

Advanced Member
Messages
5,649
I'll need a copy of the map as well.

Fonz will be able to give you more of an answer then what I can as I'm still novice, but I'll be able to spot blatent mistakes.
 
Stoo

Stoo

Whining.....
Messages
3,201
depending on which KPro you have, it may have the datalog feature built in to it

If a couple of people have had a look at the map, then they are either both missing something, or theres something wrong!
 
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fonz600

Advanced Member
Messages
575
g_mac said:
i thought it wasnt the map and it had to be something else as 2 very good mappers have had a look at it! how do you do a datalog MilanoChris an i will do 1 2nite and email it?
yea there's 2different posters, ally_mac is my bro and used to own the car, i own it now! 8)
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Connect the laptop to your ECU. Fire up KManager. Click on lightening bolt icon to start datalogging then click on red dot record icon next to it to start recording.
As Chris said earlier do a WOT run in 4th from 2k to redline.
then click red dot to stop recording. Pull over and click on Datalog tab at top of screen, then Save As. Save it under what evername you want and then send that file by e-mail along with a copy of your map.
 
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ally_mac

Advanced Member
Messages
353
fonz600 said:
How come 2 different posters are talking bout the same car? Are you the same person?
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Sorry about that mate, I am g_mac older brother and used to own the car so I am doing everything I can to help sort porblem out.

Thanks MilanoChris and fonz600 for offering to help us out, my laptop is at my girlfriends house, so I will get it tomorrow and run the datalogger either tomorrow or Wednesday at the latest. xthumbsup
 
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ally_mac

Advanced Member
Messages
353
Map and datalog sent to both fonz600 and MilanoChris. Fonz600, you may get the email twice as I entered chris email wrong first time around so had to resend it again
 
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