Jump to content
The mkiv Supra Owners Club

Vvti running too rich


Rywalls

Recommended Posts

Had the supra on the dyno at evotune and it made 384bhp at the crank.

 

I'm not sure how the fuelling or the afr is shown on a typical dyno graph but where the hp and tq curves were, the fuelling curve was almost off the chart at the bottom. I'll post up a pic of the graph asap. This was explained as the car running very rich and felt no where near as powerful as the other local bpu supras that have been on at dyno days. I was advised to fit a fuel pressure regulator to lean out the mixture which should bring the fuelling curve on the graph closer to the hp and tq curve increasing overall power.

 

It's a low mileage vvti j-spec engine full bpu:

Double decat, Walbro 255, iridium plugs, aftermarket air filter, hks bov, greddy boost controller, good condition stock intercooler and fcd.

 

Not one for chasing numbers but I'm aware healthy bpu supras make 400hp and sometimes over.

 

I have an adjustable fuel pressure regulator waiting to be fitted but is there anything else I could do with checking as I don't want to be covering up a potential problem by just fitting a fpr.

 

Thanks in advance

Link to comment
Share on other sites

I have an adjustable fuel pressure regulator waiting to be fitted but is there anything else I could do with checking as I don't want to be covering up a potential problem by just fitting a fpr.

 

Which you will be, as well as cocking up all the fuelling under all load conditions, running lean everywhere. Awful suggestion from whomever told you to fit it.

 

Stick the dyno chart up so we can see it :)

Link to comment
Share on other sites

If your BOV is not recirculation style then take it off and put back standard one. vvti have maf sensors and they dont like classic bovs. Paul Whiffin wrote somewhere (cant find that topic now) that definitely not recommended on the VVTi cars.

Link to comment
Share on other sites

Before fiddling invest in a GOOD wide band O2 sensor and readout and actually view the mixture in real time, on the road. The better ones will write a log. All 2JZ-GTE's and most other high power turbo petrol engines run very rich at full boost, it's to keep the catalytic converters from overheating. A proper, aftermarket mappable ecu will allow you to weaken it if you remove both cats, to the benefit of economy and performance. Run either the stock recircuklation valve or blank it off entirely. I haven't run a BOV or recirculation valve on a modded turbo engine in twenty odd years.

Link to comment
Share on other sites

Cheers for all the comments really appreciate it.

 

I'll get the dyno graph up tonight.

 

Thanks for the link sebas.

 

The bov is atmospheric at the moment however I do have the recirculation kit in the house on standby so I'll get that fitted.

 

You'll all know alot more than me about this so forgive me if this is stupid but, I was under the impression that the maf sensor with an atmospheric bov only ran rich because once the throttle was closed the ecu pumps a load of fuel through but the bov has chucked all the air out. So on a dyno with WOT how could the maf/atmospheric bov combo cause the engine to run rich?

 

Thanks for the info Chris, I'll get the afr gauge sooner rather than later. If it is just down to the fact that it's overfuelling with it being a vvti then will leaning out the fuel with the fpr be a safe move? I'll be getting a standalone ecu eventually ready for the single turbo conversion but this won't be for a while yet.

Link to comment
Share on other sites

I have an AEM UEGO AFR with the typical Bosch sensor which offer serial output to ECU or your laptop on my VVTi. As above, put your foot down and it goes off the dial rich. For pure octane the stoichiometric mixture is approximately 14.7:1 .

Link to comment
Share on other sites

Hi mate

 

On my old Supra TT Manual BPU I made 335rwhp at 1 bar so around 400 at the fly accepting reasonable transmission losses.

 

My AFR's were spot on too, never dipped below 11. Here's a couple of my dyno graphs measuring boost and fuelling readings which may assist you a little.

 

Good luck and hope you resolve soon with a straight forward fix.

 

image.jpg

 

image.jpg

 

Greg

Link to comment
Share on other sites

When my J spec was BPU running 1 - 1.2bar I always saw AFRs going down as rich as 10 AFR, if fact most of the jap turbo cars I have owned have done the same on full boost, if fact it one of the reasons that a lot of jap turbo cars are easy to take a bit further by increasing boost a little without having to worry too much about lean fuelling an det.

Link to comment
Share on other sites

Cheers tricky Ricky, so you reckon thats about normal then? Trouble is you're not meant to push it much past 1.2 bar with the ceramic turbos on j-specs. Mines more or less topped out at 1.2 bar now but only makes 380 hp. Any idea what options I have for a piggy back ecu for vvti to safely sort the fuelling out?

Link to comment
Share on other sites

Cheers tricky Ricky, so you reckon thats about normal then? Trouble is you're not meant to push it much past 1.2 bar with the ceramic turbos on j-specs. Mines more or less topped out at 1.2 bar now but only makes 380 hp. Any idea what options I have for a piggy back ecu for vvti to safely sort the fuelling out?

 

EManage Ultimate is a great unit for the Supra with proper fuel control mate. I think there were some issues UK specs and VVTI Supra's using the Emanage unit but am sure these were resolved. Syvecs out of your budget ?

 

Old but maybe useful:

 

http://www.mkivsupra.net/vbb/showthread.php?30172-Piggyback-for-VVT-i

Link to comment
Share on other sites

380 BHP sounds very good to me, a lot of rolling roads give wildly optimistic readings! The fuelling isn't crazy either, and was probably measured with a probe up the exhaust rather than near the turbo exits. I wouldn't concern myself about it until you start serious mods with a mappable ecu and a proper, in the downpipe, wide band EGR gauge.

Link to comment
Share on other sites

EManage Ultimate is a great unit for the Supra with proper fuel control mate. I think there were some issues UK specs and VVTI Supra's using the Emanage unit but am sure these were resolved. Syvecs out of your budget ?

 

Old but maybe useful:

 

http://www.mkivsupra.net/vbb/showthread.php?30172-Piggyback-for-VVT-i

Ah cool cheers mate I'll have a read through it. I know of people using the hks f-con v-pro gold and the hks valcon for the vvti cam but I'm sure these are discontinued now and pretty rare.

 

I am wanting to go single in future and was looking into the syvecs but this won't be for a year or two, just wanted it to be running right on full bpu first to get used to the car before I went single

Link to comment
Share on other sites

380 BHP sounds very good to me, a lot of rolling roads give wildly optimistic readings! The fuelling isn't crazy either, and was probably measured with a probe up the exhaust rather than near the turbo exits. I wouldn't concern myself about it until you start serious mods with a mappable ecu and a proper, in the downpipe, wide band EGR gauge.

You're right, 380 isnt a bad figure I suppose, just comparing it to the other local bpu supras I think I just had my hopes up for it creeping into the 400's with it being a lowish mileage vvti too.

 

But like I said I'm not one for chasing numbers aslong as it's normal and the car is running safe then I'm a happy bunny. Fmic and cams are on the list once the afr gauge is installed and the recirc kit is on so that should bump it up a tad.

 

Cheers for all the help guys much appreciated

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. You might also be interested in our Guidelines, Privacy Policy and Terms of Use.