Jump to content
SAU Community

Recommended Posts

hey guys im after a solution for my rb20

we replaced a blown head gasket a few nights ago and placed everything back on the engine, turned it on and all of a sudden its idling weird. We know that the timings out but that can be fixed. We had checked everything before it went back on. The plugs, coils, torque settings, camshaft placement etc, etc. Unfortunately after a quick compression test, my mate found out that the front bore wasnt getting enough compression. What could it be? Has anybody had the same problem before, i cant afford to take it into an mechanic atm? Soo please help :huh:

Cheers Tom

Link to comment
https://www.sau.com.au/forums/topic/256559-rb20det-running-5-cylinders/
Share on other sites

Hope you haven't bent a valve when clamping the head back down. How much compression is "missing" (compared to other cylinders)?

Have you isolated which cylinder is running crappy? have you checked that you haven't bent a pin in one of the coil pack connections?

Hope you haven't bent a valve when clamping the head back down. How much compression is "missing" (compared to other cylinders)?

Have you isolated which cylinder is running crappy? have you checked that you haven't bent a pin in one of the coil pack connections?

Thanks for your reply. Um all the coipacks are mint as ae. And its the 1st cylinder from the radiator side.

I did a 'quick compression test' without a compression tester valve by jst feeling how much compression there was in all cylinders by placing my hand over them, and i could definently feel a huge drop in the one cylinder compared to the rest.

It could be a valve, how do i be sure of it though?

Thanks Tom

So, you've disconnected each coil and determined that nothing changes when you disconnect #1?

And you need to do a proper compression test, with a gauge. "seat of the pants" measurements are useless as a diagnostic tool.

A leakdown test would tell you if its a valve or not...

However, you would need the proper guage to tell you %'s

Basically all you need to do is

- Pressurise the cylinder using an air gun and ensure nothing can get out via the spark plug hole.

- Piston must be at Top Dead Centre this way you will hear the air escape 1 of 3 ways

1. Out the plenum side = intake valve(s)

2. Out the exhaust side = exhaust valve(s)

3. Down past the piston into the crankcase = Rings

I think doing it without the proper guages though could be hard as you wont be able to measure how much or what % is escaping...

My 2 cents

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Hi Rob It's a nistune ecu. Yes same shop, good reputation. Apparently the computer on the dyno is compensated for temperature.    Chris was saying that the lean or richness of the mixture would be covered in the actual tune, but he's already picking up in advance that it's under what it should be. Regards the dyno, it's also noticeable on the road. But I just want to add something that has just come in, it appears there might be something in the setup of the external wastegate. In the exhaust manifold there is a centre divider between the front three and rear three cylinders. The external wastegate has a pipe from each side that join at the wastegate. Theory is those two pipes just might be pypassing that divider and introducing a problem somehow. Is anyone familiar with the divider in the exhaust manifold and the effects if the two wastegate pipes were to create a bypass path? Thanks for your questions Rob, interested in your thoughts on this external wastegate bypass theory. Regards Rob
    • Meh, At 60 years old, I have been doing dumb stuff for much longer than you mate, I am the true King And unfortunately I cannot be a maroon, as I am not brownish red As for not getting ITB's, the plenum intake will apparently show typical gains across the board and increase induction noise a bit, but, have all over less dort than ITB's Cost difference for the extra ITB dorts was significant though, the total parts for the plenum set up is "around" $2kAUD plus shipping, the ITB's were $4kAUD plus shipping, I was contemplating really hard about paying the extra $2k for all of the dorts, but weirdly, some form of common sense, from listening to the platform experts prevailed  As for the NA mod hate by some, I've had a few boosted cars, with all their inherent issues, I'm now looking at simplicity and legalities for a street car, maybe I'm just getting old, and I'm quite happy to spend some of the kids inheritance, 5kw at a time 🤣 And think of all the money I'll be saving on consumables that something with boost needs, like engines, gearboxes, diffs, clutches,  tilt trays... etc. etc. etc. 🤪
    • Haha.  I wouldn't say I am either but I've definitely been around it plenty.  I'm guessing you know the dial in is basically to make a handicap to level the playing field between racers.  The car with the slower dial in goes first and in theory if they run their dial in time and the faster car also does then they cross the finish time if they also have exactly the same reaction time - if you go faster than the dial in them you lose, but if you are too slow there's a good chance the other person will get to the finish line first. I'm normally supporting other cars but they were all pretty dialled and were egging me on to race as well, here's one of the cars I tune (Starlet) which ran within like 1 hundredth of its dial in through the competition: https://www.youtube.com/watch?v=inEBu-d9Gn4&t=69s
    • Where ever the fuel reg gets it reference is what I use to T into for map reference been a very long time so where it goes to plenum/runners I have no idea but never had issues. 
    • What ecu? Same shop every time? Same ambient temperature? If timing is correct then pull plugs and see if lean or rich. Dyno can also read different if they have changed ramp rate or not set tacho/speed properly  
×
×
  • Create New...