Engine hesitant under acceleration - Coil?

For classic Porsche 911 content

Moderators: hot66, impmad2000, Barry, Viv_Surby, Derek, Mike Usiskin

Nine One One
Put a fork in me, I'm done!
Posts: 1635
Joined: Fri Mar 01, 2013 11:45 am
Location: Kernow - good old Cornwall

Re: Engine hesitant under acceleration - Coil?

Post by Nine One One »

Need a higher AMP alternator
911hillclimber
Nurse, I think I need some assistance
Posts: 18926
Joined: Mon Mar 10, 2008 6:26 pm
Location: West Midlands

Re: Engine hesitant under acceleration - Coil?

Post by 911hillclimber »

Good to read John.
Been reluctant to call in case things were still a problem!
Trust all will be well this weekend.
73T 911 Coupe, road/hillclimber 3.2L
Lola t 492 / 3.2 hillclimb racer
Boxster 987 Gen II 2.9
fcd911
DDK slapper chatter
Posts: 315
Joined: Wed Dec 17, 2008 9:33 pm
Location: Shropshire

Re: Engine hesitant under acceleration - Coil?

Post by fcd911 »

Having done well over four hours of very tough night rallying with main beam and spotlights on, included some very steep accents the engine never missed a beat. Except when exiting a very deep ford (which sadly had a very quick Mini drowned out in the middle of it) there was a sudden hesitation but I think it was water on electrics, it instantly cleared.

Therefore I am confident the new coil has done the trick. In fact the night took its toll on the battery which necessitated the use of my jump pack to start the car after a very short rest halt, despite this the car still pulled like a train. A new battery may be required. There are only two events I do that run into the dark and this is the most demanding by far. Having looked at high output alternators it may not be cost effective and the jobs list for next year is beginning to grow already!!

John
DDK Member: 0471
1973 911S 2.4 Targa RHD (34 years ownership)
1973 911T (RS Rep) 2.7 RHD Rally Car (911/83 etc)
911hillclimber
Nurse, I think I need some assistance
Posts: 18926
Joined: Mon Mar 10, 2008 6:26 pm
Location: West Midlands

Re: Engine hesitant under acceleration - Coil?

Post by 911hillclimber »

Excellent!
:bounce:
73T 911 Coupe, road/hillclimber 3.2L
Lola t 492 / 3.2 hillclimb racer
Boxster 987 Gen II 2.9
neilbardsley
Nurse, I think I need some assistance
Posts: 7756
Joined: Mon Apr 16, 2012 4:31 pm

Re: Engine hesitant under acceleration - Coil?

Post by neilbardsley »

Jonny Hart wrote:You MUST use a Bosch CDI coil with our ignition boxes. The Bosch CDI coil (p/n as stated above) is unique in that it is very FAST to discharge and recharge. Our boxes exploit that speed in that we fire the coil twice per combustion which offers emissions and performance benefits.

We've actually designed our own coil which performs very well but have struggled to find a company that can manufacture them. After FIVE years of messing about and several false starts, we finally -may- have found a company that can fill and vacuum the coils properly. Bosch can't even do this repeatably anymore which is why the silver ones fail seemingly at random. Given the amount of R&D and outlay, It will probably end up being the most expensive coil in the world!
Jonny : Sorry off topic but I have recently installed a MSD CDI system in my 914 that also claims to fire twice (below a certain rpm) would it benefit from the Bosch CDI coil or MSD coil? What is the part #?

Sent from my 22011119UY using Tapatalk


“A REMINDER. I would be grateful if those members who have borrowed bits from me in emergencies (e.g starter motor, oil cooler, etc) would return them and/or contact me”. – Chris Turner RIP
User avatar
Jonny Hart
Put a fork in me, I'm done!
Posts: 1544
Joined: Mon Feb 01, 2010 2:28 pm

Re: Engine hesitant under acceleration - Coil?

Post by Jonny Hart »

IMO the MSD system spark interval (1ms) isn't fast enough to benefit from a fast coil.
Post Reply