Where has the power gone?

[ChrisGB]

Car has done 62,000 miles, most of it on very high quality oils, never thrashed cold. Modifications are to the exhaust system only (PPE manifold and decat pipe, custom free flowing absorption type exhaust). 2000 miles prior to cam change the car was dyno checked making a nominal 154bhp on the stock ECU.

The problem. Following a cam change (Crower stage 1), the power was well down (124bhp). Checking through the install, the compression ratios where down equally across all cylinders (140psi ish) all timing marks matched up, all valve clearances within limits. The vvti actuator is not locked (can be manually triggered and seen to effect the cars idle). Original cams now back in. Compression ratio is up, but takes 7 or so cranks to get up to 185psi (sluggish, should be there immediately). Leak down test shows bores to be good and valves to be seating / sealing correctly.

Running tests now show it at 134bhp with torque curve the expected shape. AFRs scan correctly with expected levels throughout the rpm range. Ignition timing is running up to around 25 deg advance at the top end according to the ecu output that can be measured.

The obvious has been checked (air inlet system and exhaust not obstructed).

The only thing I can think of is that the vvti actuator is sluggish in closing to fully retarded position (though I do not have evidence to support this and no CEL is showing).

Any suggestions greatly appreciated as this is doing my head in and costing me a lot of money.

Chris

[normanh]

Chris

Can you be 100% sure on the dyno calibration?

If you cylinder prssures where down significantly you would observe a increase I sump pressure, did you check those pressures with the engine hot or cold?



norman

[Anonymous]

6 turns is the recommended number in my compression test kit.

[ChrisGB]

Chris

Can you be 100% sure on the dyno calibration?

If you cylinder prssures where down significantly you would observe a increase I sump pressure, did you check those pressures with the engine hot or cold?



norman

 With the stage 1s in the car took 2 seconds longer to go from 60 to 80 in third than it had previously. Dyno only shows 10bhp improvement with the stock cams back in. My instinct is following my reasoning that cam timing is still not right. Could be vvti or maybe source material for intallation. Will check with installer today to verify they are using bgb / compare bgb with autodata.

Chris

[Ilogik]

I don't know if it works like the 2zz, but I read that there is like a little screw inside the 2zz that you turn and it disables vvti. Could something along those lines possibly happened? Is that the only thing to have changed? what about an exhaust leak? I know when my exhaust played up the loss of power was a mental.

Is it all on the same dyno?

[ChrisGB]

I don't know if it works like the 2zz, but I read that there is like a little screw inside the 2zz that you turn and it disables vvti. Could something along those lines possibly happened? Is that the only thing to have changed? what about an exhaust leak? I know when my exhaust played up the loss of power was a mental.

Is it all on the same dyno?

Same dyno for before and after cam change (from stage 1 to stock). No exhaust leaks.

Chris

[Ilogik]

i tried to find thet thread i read on the screw. How is your compression and leak down?

[ChrisGB]

i tried to find thet thread i read on the screw. How is your compression and leak down?

Refer to post #1 for that info.

Chris

[markiii]

any intake manifold issues?

dying MAF?

[ChrisGB]

any intake manifold issues?

dying MAF?

 Don't think so as AFRs are exactly right for stock ecu.

Chris

[markiii]

so if its fine on AFR

the that rules out

MAF
Intake
O2
injectors

you've already ruled out the exhaust

can you monitor the ignition timing?

[ChrisGB]

Tuner checked this out yesterday and reckoned it looked about right, rising to around 25 deg at the top end. He has in on the rollers today trying to make sense of it.

[markiii]

any progress Chris?

[ChrisGB]

any progress Chris?

Apart from me getting seriously knobbed off with it, nothing great. Mapper tried adjusting the ignition timing yesterday but unichip died while mapping. We have eliminated all engine wear related causes, ignition timing looks to be in the right area, fuelling is fine. This leaves the vvti controller. Either it is not returning to fully retarded or is not being monitored / controlled. Not thrown a cel, but am replacing the actuator and see how it goes.

If this line of investigation fails to fix it I am just putting it back together as is and will start saving for an engine swap. At least we know the cams were not the cause, but the fact that the problem is worse with increased duration cams points to cam timing issue of some description.

Chris

[markiii]

heres a thought vvti is oil pressure activated isn;t it?

do you have good oil pressure?

is it possible the oil pump is failing?

[ChrisGB]

If there is a vvti issue it is that the inlet cam is running too advaced. The oil pressure is used to activate advance, valvetrain drag drains oil from the actuator. We have checked the vvti advances the cam. Only concern is that the vvti is not returning to the fully retarded position. Going to cost me £112 + VAT to find out.

Chris

[normanh]

Chris

Did you resolve that issue with the dead socket for the code reader? I am sure that has some bearing on the problem!!! I am trying to squeeze out of a friendly auto electrican the wiring for the socket when he remembers it.

norman

[ChrisGB]

Chris

Did you resolve that issue with the dead socket for the code reader? I am sure that has some bearing on the problem!!! I am trying to squeeze out of a friendly auto electrican the wiring for the socket when he remembers it.

norman

Not really. Obd port is working just fine and we are using it to get info out. Wish we had not reset that cel though. May have been a clue.

Chris

[mattbrown82]

Did you ever get to the bottom of this chris? Or did you give up on the Cams.

Matt

[ChrisGB]

Did you ever get to the bottom of this chris? Or did you give up on the Cams.

Matt

The more I think about it, the more I think that it is a dyno issue. Having put the stock cams back in, performance is about right for the modifications in place. The torque curve is the right shape. Timing speed / gear increments, the car is properly fit and those following me about on the Isle of Man last weekend will vouch that it is running fine.

The reduced power on the stage 1 crowers is most likely a compatability error with the PPE manifold. The manifold is specifically designed to optimise output on stock cams.

I will be selling the cams on, as well as a used vvti control valve and actuator. The engine will be sold to fund a 2zz swap in the next month or two.

Chris

[mattbrown82]

Hmmm. The reason I ask is my intended route to achive more power from the MR2 is very similar to yours, and this incompatibility may require me to move the goal posts a little.

Apologies in advance if none of the following makes sense or patronises as I am still quite new to this engine tuning lark   s:D s:D   ...

Did you try using just the Crower inlet cam and the stock exhaust cam? From what I can gather (from a few searches on google), Exhaust manifold peformance is dependant on a number of things, one of which is exhaust cam timing.  So if, as you said, PPE did design their manifold to work with stock cam timing, this could resolve the issue?

To put the above into context, my planned route to more power was to do the following:
Install Stage 1 inlet Cam
P&P cylinder head and Skim to increase compression ratio
Have a custom 4-1 manifold going to carbon can exhaust system

However If this would be a fruitless exercise then you could save me a lot of time and money (at your own unfortunate expense  s:( s:(    s:( s:(    s:( s:(   )

Cheers
Matt

[ChrisGB]

I could have tried just the inlet cam, but I was getting knobbed off with the whole situation. Initially I wanted to go stage 2, but 1zz gearing is a waste of time for stage 2 and I would have needed a new ecu solution too. This made stage 2 expensive, so I plumped for stage 1.

If you are having a custom manifold made, just have it made for the stage 1 cam timings. The PPE is a properly tuned system, as any effective 4 > 1 system will be. With the lobe position and opening data any good manufacturer can match the manifold to the cams.

Myself, I am going 2zz as I get much shorter gearing and plenty of top end power. Cost wise, it is not much more expensive than stage 2 on the 1zz by the time the ecu and gearing are sorted.

PPE, free flow exhaust and unichip / emanage blue should see you up around 160bhp. Custom 4>1 optimised for your choice of cams could make 10bhp more.

Chris

[mattbrown82]

Cheers for pointers Chris. Definitely agree on the gearing issue with the standard box. I intend to get this sorted before I do any work on the engine as well. Just trying to get a quote from a local gearbox specialist.

Good luck with the 2ZZ build.