Hi comp b18c idle help


fatboi

fatboi

B16 EJ9
Joined
Dec 28, 2008
Messages
684
My mate has just rebuilt his jdm b18c 98spec with:
Brian crower stage 3 cams
Brian crower dual springs and titanium retainers
Weisco hi comp pistons
Think the block was bored to 81.5mm
The engine has been put together with stock cam gears and stock valve clearances to run it in before adding the vernier pulleys and mappable ecu to get it mapped.
Question is....it runs fine on choke, but as soon as its off choke it cuts out, and will only run with the idle screw almost all the way out. We have tried the iacv and tb from my engine which are known to work, and it doesn't help at all. Also, the revs drop considerably when pressing brake pedal or switching lights on, and it tends to cut out.
What are we doing wrong, as its driving us mad.
We have came to the conclusion that the bigger cams need a lot more air than stock to idle, as when my throttle body is fitted with idle screw mostly in, the car won't even start. But it will run with his tb with idle screw all the way out.
Help please!!
If you need more info let me know, I've probably missed stuff out, I'm tired!
 
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a high compression motor with big cams needs to be run in & mapped on the dyno, you can't run (safely) an engine with no map, it could run lean and blow up, or ping/knock and unless you know what your looking out for you'd never see it coming.

I would say your problem lies with the fact your trying to run a massive cam on stock cam gears, if you read the technical data it will say -3 intake -3deg exhaust or something as a base level, then somebody who knows what they are doing can play with that some what.

just my 2 cents
 
I have said that he might have trouble timing it up on stock cam gears. But when its running, it does seem to run really well. He's drove it and put some miles on it today with the idle screw most of the way out and idling just over 1k.
Does anyone know if valve clearances should still be set to stock values with bigger cams/higher comp?
 
"run really well" are you running a basemap?

I look forward to seeing melted pistons in the near future?
 
Its running a stock 98spec ecu just to run it in. He built his previous teg with completely stock everything, except higher comp pistons, and never had that mapped. Ran it on a stock ecu until he sold it, and that ran brilliantly and was ver fast until the day he sold it.
Not arguing that you wrong mate, just stating what happened.
 
joe said:
"run really well" are you running a basemap?

I look forward to seeing melted pistons in the near future?
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Too true^^^^^, how can you expect to fit a lairy set of cams and expect to run it in on a stock map?
 
Those cams should not have been fitted on stock pulleys. They come with a cam card stating where the int. and exh. valves should start to open and close in relation to angle of your crankshaft. You need to fit a degree wheel to crankshaft and use a dial indicator on valve then adjust cam gears until the cam events are as specified.

Having your cam timing correct can make a huge difference to idle quality.
 
ijwhiteman said:
As above!

This engine will melt if he carries on!
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No it wont. If he drives it sensible he will be ok. The cams do need dialed in though.
Also you should never really have to adjust the idle screw. And check the oring under it hasnt split.
 
The o-ring is fine mate. In all fairness he is only revving it to 4k rpm, and noot uinder full load.
I don't really understand how anyone would get their car mapped to run it in? As surely the car would have to be limited on the dyno etc?
I'm confused...
 
Murray said:
No it wont. If he drives it sensible he will be ok. The cams do need dialed in though.
Also you should never really have to adjust the idle screw. And check the oring under it hasnt split.
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WOW looks like we have an expert here! :lol:

If I use the wrong fuel in mine it will melt the pistons! High compression, wrong map and fuel is a recipe for disaster! We are not saying these things for the shear hell of it!

The higher compression cause the fuel to to be compressed and with a low octane cause it to ignite before the spark plugs tell it to. This is very bad because whilst the piston is still trying to travel up the fuel has ignited trying to push it back down. Like wise if the spark are not firing at the correct point the above happens regardless of what you fuel you have got. It must be mapped! Running on stock ECU is rediculous!

fatboi said:
The o-ring is fine mate. In all fairness he is only revving it to 4k rpm, and noot uinder full load.
I don't really understand how anyone would get their car mapped to run it in? As surely the car would have to be limited on the dyno etc?
I'm confused...
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When my car was built it was tuned on a dyno straight away. Modern engines do not need 1000miles of run in period. In actual fact it is not go practice full stop. Run it hard from day one and on a mineral oil. Drop the oil after 500-800 miles and then put full synthetic in if you wish. Never run fully synthetic from new the rings and cam won't bed in.

Take it to the dyno and get it tuned simples!
 
White man - all of that only happens under full load or high revs. While cruising there should be plenty of timing left in the map and a lack of any real heat to prevent any disaster I would have thought? Obviously not a good thing and should seek professional help if he didn't realise the cams needed dialing in!
I wouldn't be driving it about for the sake of it without having it half set up though this is a personal preference.

I have no real world experience so take what I say with a pinch of salt. This is just from what I've read and understand about maps/tuning. Your not going to be pulling insane timing on part throttle and this should deter anything catastrophic from happening from what I understand.

However if I am wrong then I do need to be corrected, we are all here to learn at the end of the day!
 
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fatboi said:
The o-ring is fine mate. In all fairness he is only revving it to 4k rpm, and noot uinder full load.
I don't really understand how anyone would get their car mapped to run it in? As surely the car would have to be limited on the dyno etc?
I'm confused...
Click to expand...

Personally I offer the supply of a ecu with a safe map for the particular engine setup so customer's can run their engine in prior to mapping however a lot of times the customer just lets me run the engine in for them on the dyno.
 
jesse888 said:
White man - all of that only happens under full load or high revs. While cruising there should be plenty of timing left in the map and a lack of any real heat to prevent any disaster I would have thought? Obviously not a good thing and should seek professional help if he didn't realise the cams needed dialing in!
I wouldn't be driving it about for the sake of it without having it half set up though this is a personal preference.

I have no real world experience so take what I say with a pinch of salt. This is just from what I've read and understand about maps/tuning. Your not going to be pulling insane timing on part throttle and this should deter anything catastrophic from happening from what I understand.

However if I am wrong then I do need to be corrected, we are all here to learn at the end of the day!
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Correct, the danger is at high loads(WOT)
 
ijwhiteman said:
WOW looks like we have an expert here! :lol:

If I use the wrong fuel in mine it will melt the pistons! High compression, wrong map and fuel is a recipe for disaster! We are not saying these things for the shear hell of it!
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Haha yeah i must be as i use common sense.:nice:
I dont say things for the shear hell of it either, if it can be driven safe then its ok. I would not recomend booting it at all. As its at WOT is where the damage will occur.
 
This is madness what ever happened to doing things properly! Running an engine in on a stock ECU is madness!

Good luck what ever your mate decides!
 
If he drives it around carefully without sticking his foot down he will be fine. I know as I've done it.... 4 engines later.... J/k
 
Murray should become our resident tuning/engine building advisor :)
 
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