RB20DET revs GREAT, but fails to deliver power when driving...suggestions?

[s13_240_rb20]

I have solid steady fuel pressure tuned correctly to about 38psi and it goes up to about 43 psi when I build boost (both reving neutral AND driving).

I build boost appropriately up to 7lbs. when throttling (revving neutral AND driving), but it:

---requires high throttle on gear shifting (including initial movement in 1st gear) or it will stall

---has very little acceleration power when I get heavy on the throttle. It takes forever to get up to about 4k rpms.

---doesn't seem to produce much power at all past the 4k rpm range.

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I already know to check my plugs, but I am looking for any suggestions on other stuff to check when I have the little time I get each weekend to work on it.

Thanks,

--TJ

[dtowngoalie]

You shouldn't be able to build boost in neutral... I'd say that your timing is retarded or advanced really far in the wrong way. I'm leaning towards retarded though because you have no power. Your CAS should be pretty much centered in the slots.

Also, I'm pretty sure that as you build boost your FP should raise 1:1 with boost. I.E. at 5 psi you should have 48 psi of FP. 7 psi of boost would be 50 psi of FP ect.

[s13_240_rb20]

The cas was the first thing I've tried. I've checked every possible location of the cas from one side to the other. And I'll admit, right now I can't specifically remember seeing my boost gauge go up when neutral revving....got a 4 month old baby beside me so I can't go check.

oh yeah, I know that my friend has to touch up my exhaust welding, cuz I can hear a pretty big leak from the bottom of the engine.

spark plugs and exhaust leak = weak acceleration and weak upper rpm power?????

--TJ

[PorkChopExpress]

what mods do you have on the car? do you have a wideband?

[gawdzilla]

if the plugs are bad, you will feel the car bucking as it is missing. if it just feels "slow", it is probably your timing. is the car otherwise stock? get a timing light and make sure your timing is correct.

also, an exhaust leak past the turbo won't really hurt performance. if it is leaking before the turbo, then it will feel laggy/slow depending on how bad the leak is.

[rb25det250sx]

Check the timing belt...you may of skipped a tooth or two...the check the cas timing with a timing light.

[s13_240_rb20]

It's pretty stock all the way around...just a FPR, FMIC, and some gauges.

--TJ

[PorkChopExpress]

It's pretty stock all the way around...just a FPR, FMIC, and some gauges.

--TJ

oh, how about putting the fuel pressure back to stock and see what happens.

[WhatsADSM]

First things first check for vac/boost leaks and check your timing.

[Bluefire]

Your problem is right in your title "RB20DET"

seriously though, check your timing with a timing light. Also are your knock sensors hooked up?

[s13_240_rb20]

oh, how about putting the fuel pressure back to stock and see what happens.

OK...weird as I think it is that the fuel pressure jumps sky-high when I start the engine, I went ahead and turned it down to stockish 38psi with engine running.

It still ran like crap on the way to work, so when I got there, I pulled the fuses I installed between the battery and the 2 wires running to the ECU (power and memory). Waited one minute and reinserted them (to clear the ECU memory??). On the way home it felt awesome; it revved way up and still had power, shifts so much better with it running well. I even dropped back down and hammered 2nd gear doing about 40mph. Both tires on my hardbody open differential spun so fast that within a second I was about 40 degrees sideways.....surprising for an open differential.

But I don't know what did the trick: the fuel tune or the ECU memory clearing....probably the clearing because when my car had bad days like that, I just had to reset the ECU the same way...... ?????

Now if only I can figure out what annoying noise is coming from my transmission area....see other thread.

--TJ

[s13_240_rb20]

Well it is very torquy in the bottom end and very fast through the middle (thought just a mini-tad rough, I think). But it still hits loses power at about 6k...just stops accelerating.

I've been playing with different positions of the cas and I made double sure my FP is set to 37/42 to get it to run this well....

Is there any guessing which way I should turn my CAS if the power loss is on the top end? That is, if it is even related...??

Also, whenever I get my datascan working in this ride, what should the timing read on the screen at idle (say about 1200rpm)??? Anyone that familiar with datascan??

--TJ

[s13_240_rb20]

Well today I went out for another true test drive and tried to "push" against that sorry top end of the gears and I figured something out.

I thought I was lucky that fuel pressure had not been an issue (according to my gauge) using the stock hardbody fuel pump. However, today when I "pushed" (kept the gas pedal down without speeding up any) against the lack of power long enough, I saw the gauge drop.

So one day soon, I get to drop my tank and swap in my walbro from my 240sx setup and I am going to run better wire to it at the same time, cuz I do NOT want to drop it twice...lol better safe than sorry...

--TJ

[craz4240]

Do that and run a relay to get direct switched power from the battery as well.

[s13_240_rb20]

Do that and run a relay to get direct switched power from the battery as well.

I've already had it wired to direct switched 12v. I put in new premium gas and it ran great for about a week after I reset the ecu...now I have the same problem again.

I don't think I have driven it enough to use $25 worth of gas, but my gas gauge doesn't work, so maybe I am just low on gas again. I will try to refuel and see what happens next time I have it off of the jackstands.

There are 4 very interesting videos on the linked page below. You'll see good low rpm power, but poor high rpm acceleration, except when I shifted down to 2nd gear doing 50 on the interstate. It feels like 150hp instead of 200hp+....

http://s268.photobucket.com/home/s13_240_rb20

--TJ