ChrisGSR

Hey, following up on a near-disaster a few weeks ago. I had changed the timing belt in a B18C1 GSR, but due to some incorrect reference info, I put in a B18C5 belt instead, which is a few cm longer.

The engine ran horribly at first, with lots of distributor lug rattle from the lack of tension. Finally realized with HA-net members' advice what the problem was. I threw in the quick fix of having an assistant pull up on the tensioner spring during the belt tensioning process. That took out enough slack to smooth out operation and the car has been a reliable daily driver since.

It bogs at part throttle, though: timing discrepancy. Looking at the index marks, when the cams are at TDC1, the crank mark is maybe 2 degrees counterclockwise from its own TDC1 mark. This is presumably due to slightly different tooth spacing on the B18C5 belt versus the B18C1 engine. I've played around and retensioned a few times, but it always ends up the same way.

My options seem to be to get adjustable cam gears, or just put in a new correct B18C1 belt. I think I'll get the new belt.

But I noticed when shopping for the belt that some manufacturers, like Greddy with their new extra-strong belts, have the same model number for the belt for the -C1 and -C5 engines. Huh? What's up with that? Presumably something is getting traded off in the fit department. Maybe these belts don't fit either engine perfectly.

Kai

The belts should be exactly the same... :thinking:

Snoopy

exactly :thinking:

Kai

Not bad for a drunken post. :fawk:

PHiZ

Doesn't what belt you use depend on what Oil pump you're using?
-PHiZ

ChrisGSR

Thanks for all of the replies!

Anyway, yeah, PHiZ's thought was also my first guess as to why the Type-R B18C5 timing belt would be longer -- I figured it must be a higher capacity oil pump with a larger radius drive sprocket than the one on the B18C1.

As I recall, I looked at the part codes for the GSR and Type-R, and the oil pump was the same, so the guess is wrong, and the reason for the longer R belt is still a mystery. Anyway, I -do- have the belt part codes:

The B18C1 GSR timing belt is 14400-P72-004.

The B18C5 Type-R timing belt is 14400-P72-014.

Note the slight difference in the last three digits. Visually, the two belts both have the alphanumeric 126RU26 stamped on them. But the R belt is slightly longer than the GSR belt. I recall it as being maybe 3cm longer, or just over an inch for those of you who prefer Fred Flintstone units to metric.

I had been informed (incorrectly) from several different authoritative sources that the R belt was compatible with a GSR engine. When installed, it was too loose, and caused loud rattling of the distributor drive lug.

That was partly solved by adding extra spring pull on the tensioner at the end of the belt install process. But, because the belt is still slightly longer than what the other components are set up for dimensionwise, it means that the cams and the crank are slightly out of sync once everything is pulled tight.

With the belt tensioned and the cams at TDC1, the crank is a few degrees (2 or 3) past its own TDC1. So effectively, the cams are retarded, yar? This has made the car boggy at low revs. But it's also got it running happily on 89 octane midgrade, without pinging, which it would previously not do.

I want the low-rpm throttle response back, and I don't mind paying for premium fuel, so I will have to fix this up somehow. Adjustable cam gears should work. Or a belt of proper dimension.

I mentioned Greddy in the first post. Called them last week and said, "Hey, you guys have the same belt listed for the B18C1 and the B18C5, that's different from Honda/Acura practice, and I have seen from experience that they're not perfectly compatible, what gives?"

The Greddy guy mumbled something about how the B18C1 and the B18C5 belts both have the same number of teeth, 126, and so that's what their belt has.

I verified with my old -C1 belt that it does in fact have 126 teeth, which is, I would bet, connected to the "126RU26" code printed on it.

The -C5 belt now in the car has the same 126RU26 code (even though its part number is different). I haven't counted teeth, but I would bet it's also 126. However, that doesn't guarantee compatibility -- for perfect compatibility, the tooth count has to be the same, AND the intertooth distance also has to be the same.

Since the -C5 belt is noticeably longer, its intertooth spacing must be fractionally bigger. Not enough to cause an issue with the sprockets, but adding up 125 little increases in length over the whole belt gives that extra inch of total length.

As for why this length discrepancy exists, I have no idea. I did look at all of the items in the B18C5 belt path, assuming that one of them must be bigger in radius, but again, I didn't find anything that was different from the B18C1. Really weird.

Anyway, I came to this car from an SR20DE powered Nissan (tragically destroyed by an idiot red-light runner), and that had a timing chain, and man, do I miss chains. It's good to see that Honda is finally figuring out that belts are second-rate technology, and moving to chains in the newer i-VTEC engines.

MrFatbooty

The B18C1 and B18C5 have the same block casting but different heads. Perhaps the C5 casting places the cam gears slightly higher than the C1.

jmeadowszm

The gsr water pump is smaller than the type r, which since the gear on the type r water pump is larger it then turns slower at higher rpm, leading to less resistance. You have to match the pump with the belt, but either setup will work with either configuration, even ls, and b20 vtec, but the b16 requires b16 timing belt due to the deck hight of the b16 block.