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Afr With Bigger Turbo (hx35/40)

waxer52

By waxer52,
in Engines & Forced Induction

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waxer52 Enthusiast

waxer52

Posted
Posted

I have just finished putting a hx35/40 onto my rb25/30. When I had the standard turbo on the afr at idle and up through the map was pretty good.

All I did was change the turbo and now the afr is fairly lean (idle at 15.9 and comming on boost about 14.0).

I thought the airflow meter would read more airflow and adjust the fueling accordinly but it seems asthough I will have to adjust it all through the rev range.

Does this sound right, will it give lean readings just by changing the turbo. I know I will have to map it but ithought fuel was added relative to how much airflow was.

What is the best way to adjust the whole map, rescale the airflow voltage or increase injector %.

I have all supporting mods but a standard r33 airflow meter.

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JonnoHR31 Grand Master

JonnoHR31

Posted
Posted

if you have datalogit and a wideband then all you need now is the knowledge and you can tune the car yourself. set the injector % to suit the injectors you have and leave all the airflow voltages at 100%

then go into your fuel map and add plenty of fuel in every cell below p10. then start logging with your wideband, best way is to just log your aux inputs and advanced, dont worry about basic and sensors etc. do a few low rpm runs with a little boost and make sure its rich enough before you go revving it out. theres a few good excel spreadhseets for turning logged afr's into a new map instead of guessing and having to change every cell manually. look in the files section of the datalogit e group (should have access if you own datalogit).

other than that just do plenty of reading, all the info you need is on this site and the datalogit e group

standard airflow meter might run out of resolution, try the lowest boost you can to start with

Cjmartz2k Proficient

Cjmartz2k

Posted
Posted

Yes, of course he needs to get it tuned, and he already admitted it. Now that everybody is done repeating the normal line, why don't we read what he posted again and reply.

His a/f's shouldn't change at idle if all he did was bolt on a bigger turbo. That doesn't make any sense. Bolt on a T88 and as long as you aren't changing injectors, cams, MAF, etc., it should idle the same. Something else had to change to do that. Might be worth looking into before he gets it tuned. I'm not saying it's what's going on, but what if he developed some kind of exhaust leak and that's why the wide band is showing leaner. Should he still go out and tune with that equipment with the wide band being "off"?

OP--what kind of MAF voltage are you pulling at idle compared to the stock turbo? BTW, you are going to need a Z32 MAF for that turbo. I had that same turbo (loved it) and was hitting 4.9-5v at around 1.6 bar with it on a Z32 MAF, so even a z32 MAF is going to be about at it's limit, but it'll work. That stock one needs to go. Also, I just noticed you have an RB30/25. That actually might be much to small of a hotside for that turbo. I'd be looking in to a full HX40 at some point if it were me IMHO.

waxer52 Enthusiast

waxer52

Posted
  • Author
Posted

My exhaust might have a small leak where it connects with the v-band clamp.

It has now started to have an erratic idle when warmed up. Boost gauge bounces up and down a small bit (0.1bar up and down)

This thing is driving me mad. I dont want to take it to one of the three tuners in my country because i dont trust them.

Any help on what causes an erratic idle.

I have checked:

Fuel pressure-ok

cas-ok

afm-tested voltage increase as you blow air through it-ok

wasted spark setup-ok

new ngk plugs heat range 6

walbro pump-ok

no sensor faults on pfc

CEF11E Veteran

CEF11E

Posted
Posted

what size are your injectors?

I have a 7 blade HX35 on my rb30det and now have it tuned and running smoothly. I am running an external gate, 740cc injectors, z32 afm, stock modified manifold ect. How far is the Z32 away from the turbo?

I had issues having the Z32 to close to the turbo idle would hunt and was a bit erratic. I put an intake pipe in with a 90deg bend and about 45cm from snout to afm. I also removed the silencer ring from the front of the turbo and think this made a difference to idle quality.

I think it has something to do with the fact that the turbo has a 4" snout and the amount of turbulance in the intake pipe.

as for your afr's make sure you do not have an exhaust or vacuum leak somewhere.

keen to see your results!

cheers!

waxer52 Enthusiast

waxer52

Posted
  • Author
Posted

Cef11e i followed your install closely and have roughly the same setup. 550cc injectors, silencer ring (dont know if its there or missing), the standard airflow meter is mounted about the same distance away as standard at about 30deg angle.

It seems as though when hot it will idle fine until you blip the throttle then it becomes erratic.

I have searched for vac leaks and have found some and repaired them.

My exhaust leak is past where i have the wideband sensor mounted so it cannot be that.

It just gives a constant 15.9 afr in the off boost cells, ratios start to richen up as it comes on boost.

I think i'll try the 90deg bend on the afm next.

CEF11E Veteran

CEF11E

Posted
Posted

I posted a huge reply to this but it got lost in the ether...

here is a sum up

I posted a huge reply to this but it got lost in the ether...

here is a sum up

the K value is probably wrong. Here are some tips that may help…

1. disconnect the o2 sensor to the ecu

2. plug in the wideband and start the car and monitor the AFR’s. if they not 14.7 the K needs to be adjusted till its close ( less than .05 afr out) do this when the car is warm so cold start does not affect the afr.

3. once the AFR is correct on idle plug in the o2 again and drive the car logging afr’s and compare them against the map. They should be very close.

4. adjust every cell in the last 3 colums above 3000rpm to 11.5:1

5. adjust the primary timing map to 14deg in the last 3 colums above 3000rpm

6. adjust boost to 10psi or less. drive the car logging afr’s thru all rev ranges to 5500 on varying loads. Compare AFR’s to the accompanying load cells. Adjust as needed.

7. you can now put the car on the dyno and start winding up the boost. Tune to desired boost level.

8. road test the car full throttle in 2nd 3rd and 4th. Monitor for knock. Also boost up a hill in 2nd to 6000 fully decelerate and then when revs die to 3500 mash the throttle and monitor knock. The cells between 3500 and 6000 should be no leaner than 11.5:1

9. put the car back on the dyno and do a power run, monitor final afr’s and you will have your power figure 

the turbo should make full boost by about 4000rpm and make 350rwkw.. huge fat power curve and climbing all the way to redline!

waxer52 Enthusiast

waxer52

Posted
  • Author
Posted

Ok im trying to sort this out but not great. the idle is fine under cold start and my throttle sensor voltage has been adjusted to 0.45v.

When the car is just about warm 78deg water temp you can give the throttle a blip and when it returns to idle it starts to hunt. Its like a restriction on the inlet, i think it may be the aac valve. If i try to set the idle on the aac valve by turning the screw it has no effect on idle so i think it may be f*****.

I can get the afr to come down at idle be rescaling the afm voltage, but im not sure if this is the best way.

Any help on this greatly appreciated.

STATUS Grand Master

STATUS

Posted
Posted
Maybe a silly question but you refer to the k value, whats this?

Thanks cef11e thats the best explanation i have had .

k is remap jargon :)

its not relevant to pfc, adjust your inj corrections whnevr you read K value above :cool:

Cjmartz2k Proficient

Cjmartz2k

Posted
Posted
If the aac valve is stuck open would this be the cause of my lean afr. It would be dramwing extra air and so lean out the afr. Not sure what else it could be.

Starting to get annoyed with it now.

IAC valve should still be pulling metered air, so I don't think so.

Mr Jollwah Community Regular

Mr Jollwah

Posted
Posted
If the aac valve is stuck open would this be the cause of my lean afr. It would be dramwing extra air and so lean out the afr. Not sure what else it could be.

Starting to get annoyed with it now.

Have you checked the inlet pipeing from afm to turbo, may have a leak.

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