Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Incredibly violent banging under hard acceleratio?

Good morning Greg. Having owned from new and driven 9000 miles in a 2016 M3W, I'm a little alarmed in this thread and another you started that so little consideration is being given to the running-in process which as already mentioned is ECU controlled up to 20 hours on the engine. Your initial comment the engine wouldn't rev beyond 5000 rpm and now full throttle issues in low gears with only an hour or two on the engine raise further concerns! My own thoughts are that extreme early hard use has highlighted a bevel box location issue. This could be as already suggested, a loose NVH mount which cushions the location of bevel box or even a broken mounting lug for same. Either way the considerable torque reaction from the engine is likely smashing this box against the chassis giving rise to the horrendous sounds you are hearing and feeling. It may be solved by tightening drive belt but I never had to touch mine during the two and a half years of ownership. To give you a guide, when new tension was such I could only twist top of belt through maximum of 30°and was still exactly the same after 9000 miles.

As suggested Phil Bleazey is the man to contact for long term solutions to the M3W drivetrain he has developed, although in the short term, a visit to your dealer for belt tension check or warranty work if more serious problems are found may be in order. I wouldn't mention to the dealer your early hard use though if you want the factory to cough up on possible repairs.

Must admit Richard I cringed a bit when reading it won't go above 5000 rpm with just a few hours of running😲
I think these engines do need careful running in and also warming up before hard use. Although I tried to adhere to this, when I picked up my M3W from new I had a 3hour motorway drive home, I tried to keep the speed down and vary the revs but I recon this is what damaged the bores causing it to need new pistons and barrels at around 2000 miles. Could of course just of been one of those things but the engine sound definitely changed on the way home becoming more tappety. Didn't make that mistake with the new barrels adhering to S&S running in recommendations👍

Just as a quick update, went for another spin today and even under mild throttle I had a pop a couple of times when I didn't get off the clutch smoothly enough that, after hearing you guys, could certainly have been the belt slipping a spot. So the belt is either loose or the bevel box is moving more than it should creating that slack under load. I'll try to nurse it until first service and have them check both.

As for the break-in, I'm mostly cruising aroung around the 3k mark but have run it up through the revs a few times. (I was immediately deterred by the banging!). The range of revs and loads is modest but certainly not out of a lack of consideration, in fact it's deliberate as I want a good bedding in of the engine.

To put this in context, my usual way of running in engines is to run them flat out for the first 50 miles, under load and through all revs, preferably with non-synthetic oil, then change to synthetic, and job done. Most break-in procedures are a myth IMHO. I've seen poorly maintained high-compression diesel engines with half a million miles on them and you can still see the boring marks from when they machined the cylinders! The first few miles are the most important, but to create a good seal between cylinder walls and piston rings. If you wait 500+ miles before putting load on the engine the rings will already have hardened and never expand properly. You will have poor compression, blow-by, dirty oil, and oil consumption.

Call me crazy but I do this to all my cars, have never had a wear issue despite them all being tuned to rev higher than stock, going on plenty of track days, they have above factory-spec compression even after 150k miles in one case, and they don't need a single oil top up between 15,000 mile services. They've always dyno'd above manufacturer specs too.


Granted I'm not familiar with S&S but I assume they don't chissel the cylinders out of a block of cheese, or am I mistaken?

(Though I am religious about warming engines up properly and NEVER lugging if that helps)

my belt was horribly loose (from the dealer) and would make such a noise, but on deceleration. It was not skipping, but slapping.

Well that is contrary to S&S break-in procedures but I guess you know what you are doing.

+1

Definitely see where your coming from Greg with the ring bedding but as some of the engine parts are In f act made of cheese you do have to be careful 😂
I had the same problem with banging that you’re describing which was cured with Phil Bleaseys bevel box mount.

Here is the video

http://www.youtube.com/watch?v=Q36-b0pG2mA

After how many miles was this NVH movement evident?

I think I did that around 3k miles. How the NVH is attached to the front of the bevel box it will never be any good.