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I took my new VE to the dyno this morning. I work on a Dyno Dynamics Dynamometer which, I believe, reads about 5% lower than some of the other more commonly used models. So I was hoping to put down around 170WHP with my new used engine. My set up is DE MAF and TB, JWT ECU, VE injectors with a Fuji header, HS CAI and 2.5" exhaust.
But there were some interesting things that I found out. Before I get into the story, here is an image that shows one of my better runs compared to my old engine with S3 cams.
Now on to the story. My first run was with the fuel pressure set at 46psi with the vacuum hose disconnected. All subsequent fuel pressures that I mention in this message are with the vacuum hose disconnected. This first run showed a very lean mixture (high 14s and even a couple readings over 15). Also, the engine was falling off above 6500 RPM -- well before the rev limiter kicked in.
I raised the fuel pressure to 54 psi for the next run. The AFR fell more into the acceptable range, but on most runs, the power would fall off 10-15WHP above 6500 RPM. Sometimes it would surge up again before red line, sometimes not.
Watching the fuel pressure gauge during a dyno run showed that the fuel pressure would start to waiver around 5000 RPM and then would fall as much as 5-6 PSI before the run was over. In other words, I would watch it flicker as the cams came on, then it would fall from 54 PSI to 47-48 PSI before the run ended.
It did not seem as though the engine was misfiring, it just went soft, and the fuel pressure would fall. In the dyno chart that I provided above, you can see the mixture getting leaner between 6000 RPM nad 7000 RPM, but this is one of the runs were the power did not dip. My dyno operator is a BMW guy, but his guess was that my fuel pump might be marginal.
What do you all think? Should I try a new OEM fuel pump? Have any of you upgraded to a Walbro?
Thanks for your input. I'd like to get this car healthy for the Convention.
Bill Conner
UPDATE March 7, 2005:
Installed new Walbro today and set the fuel pressure for 5 pounds above OEM at idle with no vacuum. When I went for a test drive, I found that the problem had not been resolved. At about 6800 RPM (indicated), the engine stops pulling and loses power. It just kind of goes soft. This happens just about all the time in third gear and sometimes in second.
Then I swapped in a different MAF and found no improvement from this change.
Then I put in the original MAF again and hooked up the Nissan Data Scan software. Here is some of the data that I acquired:
MAF at 7200 RPM in 2nd gear -- max reading was 4.51V
MAF in third stops climbing around 4.3V when the engine goes soft
TPS is .48V at idle and 4.18V at WOT
Injector duty cycle max was 62
O2 voltage swings back and forth frequently until you get on it -- then it stays rich.
Finally, I unhooked the cam solenoids and ran it up through the RPMs to see if she would go soft. But it seemed to pull all the way to red line with no problem (though slowly). Max MAF reading on low cams was 4.3V at 7200 RPM.
I'm wondering if maybe one of the solenoids is letting a cam fall back to the low cam in 3rd gear -- but I'm not sure how to check for this or what I would do about it.
Stock cams? 165whp on a DD dyno is not bad at all. Adding the 5%, that's 173whp on a DynoJet. I think the DD read much lower than 5% from a DynoJet. A friend of mine does a lot of tuning on one, and I was trying to ask him the general % difference, but he didn't answer his phone. With stock cams and a cat, I think you are right where you need to be. It also looks like your cams are switching at 4200 and 4700. I would move those up a little. I would try 4500 and 5200. Mine are 4500 and 5500, but I have SR16 cams.
Stock cams? 165whp on a DD dyno is not bad at all.
I agree, I'm not all that disappointed with the overall power output on a good run. It's the lack of consistency that concerns me. More often than not, the WHP would drop 10-15 units above 6500 RPM. It's a dramatic dip. Now that I'm aware of it, I can feel in on the road. I'll try to graph some of the data and post it, but I did not get a representative graph printed.
BTW, Eric, you have a heck of a good eye for picking out the cam activitation points. You were dead on. I moved than back from 4800 and 5200 to remove a flat spot in the WHP curve. It worked pretty well. I figure I will not bother fine tuning the switch points any further until I get this other thing worked out.
I'm guessing you have the timing at 15 deg, correct? How does the car run on the street? I'm going to dyno mine on a DD dyno soon. If you bring your car to the convention, we are going to have a ton of VE cars. Mine, yours, Jason, Matt, Serban, and maybe a few others.
Given the lean conditions, I'd look at a Walbro. I have one in my b14.
I'll probably be driving my VE b14 to the convention, as well.
We have a Dyno Dynamics dyno at the shop and I find it reads very comparable to a Dynojet. I would say no more than 5%. Some people throw around as much as 15%, but that's bogus. I'll be tuning my car some this week (the b12) for a race this weekend for the first time on the DD, I'll give you a more concrete answer then.
I'm guessing you have the timing at 15 deg, correct?
Eric96SER -- I was running at 17degrees BTDC until I went to the dyno. At this point, I am actually getting the best output at 13 degrees. I will check timing again on the dyno once I get the inconsistent output at high RPM straightened out. It feels pretty good on the street now -- but I can feel the drop in output at high RPM now that I am looking for it.
Quote:
We have a Dyno Dynamics dyno at the shop and I find it reads very comparable to a Dynojet. I would say no more than 5%.
Big John -- I think 5% is about right. I did a straight comparison between the DD and a Dynojet about a week apart on my car when I was running S3s. Over most of the RPM range the difference was 3-5% but it ran as high as high as 7% at the top of the range.
Quote:
I put a Wlbro 190 lph pump into my VE (94 B13). It wasn't needed that I know of, but I didn't have enough faith the old stocker.
Jacen99SE -- I ordered a Walbro 190LPH today. My car has over 100K on it and the stocker may be marginal. If the Walbro doesn't straighten things out, I thought that I would swap in a used MAF that I have hanging around to see if that solves the problem.
Any other thoughts, guys? It will be a week or more before I get back on the dyno, but I will report back in with the results.
Jacen99SE -- I ordered a Walbro 190LPH today. My car has over 100K on it and the stocker may be marginal. If the Walbro doesn't straighten things out, I thought that I would swap in a used MAF that I have hanging around to see if that solves the problem.
Any other thoughts, guys? It will be a week or more before I get back on the dyno, but I will report back in with the results.
Bill
Good, I think you need a new pump. Check you pressure at idle with and with out the hose connected. Then try it with the car not running but turned on. I was told that is actually the most consitent way to check the base fuel pressure.. That way idle speed, etc does not effect the reading. I would be curious to see your results.
Offtopic, If you have a JWT VE ecu program for the VE injectors, why didn't you go with the VE MAF? I would think that would have helped your numbers a bit.
I thought that I would swap in a used MAF that I have hanging around to see if that solves the problem.
Any other thoughts, guys? It will be a week or more before I get back on the dyno, but I will report back in with the results.
Bill
I would check out the MAF too. I think your issue is either a fuel pump, or the MAF. My old motor never made the power it should have, and I think the MAF was messed up. A new fuel pump never hurts, so I would start there first.
Offtopic, If you have a JWT VE ecu program for the VE injectors, why didn't you go with the VE MAF? I would think that would have helped your numbers a bit.
Thanks for your suggestion. When I ordered the ECU from JWT, they swore up and down that the VE/Pathfinder MAF and the DE MAF produce the same power. It's hard to believe when you look at them, but that's what they told me (it was Ben).
So I took the easy way out -- and used the DE MAF. I really don't know whether it would make a difference to go with the VE MAF.
Check you pressure at idle with and with out the hose connected. Then try it with the car not running but turned on. I was told that is actually the most consitent way to check the base fuel pressure.. That way idle speed, etc does not effect the reading. I would be curious to see your results.
Steve --
When I installed the NISMO AFPR, I set it up to mimic the pressures I was reading with the VE FPR: 36 psi with hose connected at idle, 46 psi without.
This is how I ran the first run in the dyno which was very lean. So I increased the pressure to 55 psi with the hose disconnected.
After a few runs, I noticed that the pressure had fallen off to 52 psi (no hose at idle). So I cranked in 3-4 more PSI. I always adjust the pressure on the dyno with the hose disconnected to remove any effects of changing vacuum or idle speed.
It was at this point that I watched the pressure gauge during a few dyno runs. It would hold around 55 psi at wide open throttle until around 5000 RPM. Then it would start to waiver and fall off to around 47 psi before the run was over.
Following your recommendation, this evening I turned the car on but did not start it (actually my wife did this while I watched the gauge). The pressure went to 54 then fell quickly to 42 where it held pretty steady.
Then I took the car out for a spin to warm it up. Upon my return I observed the following pressures at idle: 49 psi with vacuum hose connected, 59 without.
What I'm finding here is that the fuel pressure is not very predictable or constant the way my car is now configured. This could be caused by a failing fuel pump, but I'm no expert and have no direct experience with this kind of problem. I guess it could also be caused by a bad AFPR -- but this one is right out of the box and the fuel pump is 12 years old.
When I installed the NISMO AFPR, I set it up to mimic the pressures I was reading with the VE FPR: 36 psi with hose connected at idle, 46 psi without.
This is how I ran the first run in the dyno which was very lean. So I increased the pressure to 55 psi with the hose disconnected.
After a few runs, I noticed that the pressure had fallen off to 52 psi (no hose at idle). So I cranked in 3-4 more PSI. I always adjust the pressure on the dyno with the hose disconnected to remove any effects of changing vacuum or idle speed.
It was at this point that I watched the pressure gauge during a few dyno runs. It would hold around 55 psi at wide open throttle until around 5000 RPM. Then it would start to waiver and fall off to around 47 psi before the run was over.
Following your recommendation, this evening I turned the car on but did not start it (actually my wife did this while I watched the gauge). The pressure went to 54 then fell quickly to 42 where it held pretty steady.
Then I took the car out for a spin to warm it up. Upon my return I observed the following pressures at idle: 49 psi with vacuum hose connected, 59 without.
What I'm finding here is that the fuel pressure is not very predictable or constant the way my car is now configured. This could be caused by a failing fuel pump, but I'm no expert and have no direct experience with this kind of problem. I guess it could also be caused by a bad AFPR -- but this one is right out of the box and the fuel pump is 12 years old.
We shall see what effect the new fuel pump has.
Bill
I have found the same thing. Base fuel pressure seems to vary somewhat. I did not check it for a year and then BAM way different then I thought it was. So I would keep the kind of notes you just took, Check it every couple days and see which method is the most stable (never did this myself). That way after you dyno and set it to the pressure you want you have a good reference for the future.
I've never considered the need for more fuel pressure, through a Walboro or FPR. Is everyone here running one or the other, or both? (Hopefully this does not misdirect the thread).
The fact that the pressure drops and is variable at high revs means that it is not flowing enough to hold up the pressure, you cannot tell what is happening to the MAF or anything else untill that is sorted. If the MAF voltage goes too high the ECU jumps to really-rich-mode to protect the engine, as you are lean that makes me think you are not yet there on the mAF voltage.
