hey i have noticed my 3.5 swap doesnt seem to have a lot of downlow power...to the point where i hit 2nd gear it seems like it falls flat on its face. the top end power is great, but it just seems to lack down low.

i will step on it in 1st rolling, it will light up first gear. i hit 2nd and it bogs until like 5k then all after that its quick as ****. or maybe its just a weak point in the powerband and compared to the rest of it i could be exaggerating. i was wondering if others have experienced this? i have done the SSIM, but i cant see that making a large difference. any insight on this? could this be a result of timing being slightly off or would i noticed the timing being off? i have driven the car 500 miles since the swap and no problems with the engine, seems pretty quick to me.


EDIT- i also did a port and polish lower intake manifold myself. obviously im not the best porter, i followed a few DIY'S, could this affect it also? seems alright to me although i did have a hard time getting it really smooth after.

 

First item that comes to mind is the lack of CVTC. But, then again, you really have no proof of any lack of anything. Get a dyno, and proceed from there.

 

dyno was my first thought also. i will have to do that this coming weekend. thank you.

 

nismology's first

It could obviously be a number of items. But unless you really know what's going on, without a dyno, it's very hard for someone on here to help since most of us are not local, we need some type of feedback information in order to help. A 1/4 mile run (DA included) or a dyno run (DJ SAE CF preferred) would really help in this situation. That coupled with perhaps some OBDII logs.

 

yea looks like ill have to hook up my lm1wideband and snapon scanner to start with and see whats going on exactly. i was just being curious as to if this was a common problem with this engine/transmission setup. ill get back once i have some information of my own to share. thank you.

 

Check the base timing either with a scanner or timing light and try to get vacuum readings at warm idle, if possible.

 

im still going to get vacuum readings and check timing but i did a few things.

i found out i was leaking fuel and i didnt put my nitrous nozzle in the intake, so this fuel leak and vacuum leak could have been affecting performance. since i have fixed the fuel leak, re-adjusted fuel pressure to 53psi, and installed my nitrous nozzle.

i also believe this to have happened because i have not 'launched' the car...i would casually bring it up in rpms and shift...for the first time with the 3.5 i launched it, and it pulled wicked hard from a launch up to like 60 or so on a highway entrance ramp. no apparent bog or nothing. i didnt wanna take it any higher because i dont like going too fast on public roads. especially crowded ones during the day. but the 1-2 shift def. feels good when i launch it.

 

I have a 3.5 6speed and I can tell you that my car pulls in 2nd as hard as it does in every other gear. There is no bog in 2nd even when I baby shift it at 1200rpms. Not sure we can compare the swaps to the stock and obviously with your mods I may be out of line even posting.

 

Invalid comparison in many areas, this is just one reason why.

 

I sense a perma ban coming...

Nmex and OP, sorry about the previous post it may not be a fair comparo like I eluded to...good luck

 

Now where were we?

 

yes this is exactly how my car is you described it 100% right .

all through 1st gear its nuts ,but its dead below 4500-5000k in second but if i shift into 2nd from a 1st gear redline i get lots of smoke over 30 mph on the road.
But i have to say i think its just because over 5k it comes to life many say to me i have a "honda powerband" and i believe that i still have more power downlow than a USIM vq30. but the contrasts of each end of the powerband make the low feel worse than it is.

 

Like has already been mentioned, gutted IM + no CVTC = relatively lifeless until 4k+ RPM. But it's till much better than a 3.0 down low by virtue of it's geometry alone, as it's likely swallowing LESS air than a 3.0 at those RPM's.

 

I got the same exact problem as u guys. I think w/out vtcs under about 4500 rpms everyone w/ the 4.5 swap can relate w/ us. I am currently doing more research on solving the problem but I havent been tuned yet so needless to say the true potential of my car is yet to b seen. I definately have to get a jim wolf ecu to raise the rev limiter so that I stay closer to the meaty part of the powerband. Maybe I will go to nissan and have them adjust my base timing. I also heard the SSIM makes you lose a little low end also so that can b a contributing factor but I still plan on doing that mod regardless. If u guys have any more suggestions keep up coming, us 4.5 will get through this.

 

.

 

Wheels are being reinvented.

 

Ok, let's reinvent the flat tire.
IBmodpleasedelete

 

Its seems as though its a common problem among the 3.5 swap because my car is doing the same thing and maximus_95 described the same problems to me about his ride.
My car had a WHOLE lot more torque when the swap was done. Now, it tends to hesitate when the rpms are below 4500rpm's. Another problem i'm facing is that if I give it WOT during idle, it bogs and remains around 500rpms and throws out black smoke (running rich) I've checked the TPS sensor and it reads at .5 at idle and 4.7-4.8 at WOT, which is within specs. I thought that maybe the weather and a dirty as* air filter could contribute to the bogging.
I, like others, have not been tuned yet but will be doing the SSIM mod, re-do my 3 inch MAF, and get a new K & N filter, and then get it tuned... hopefully its just a fuel issue that can be resolved by the VAFC fuel corrections.

I've checked the gaps in my spark plugs and everything looks okay... I still need/want to check the timing on it to make sure its okay....

 

Wow, there is so much for me to agree on in this thread about the powerband/ Here's my take or description of my car, seems to fit in with others. It's better than the 3.0 everywhere, except between 3200-4500 it feels about equal, and after 4500 it screams all the way to redline, it feels like it would love for you to extend that revlimiter.

 

That has since been found to be foolish. I'm running stock 3.0 specs, ie I have a vacuum hose connected to my aeromotive and I'm running 43psi/34psi @ idle per the fsm, driveability = good.

 

Is your IM stock?
When @ idle w/o AC I need to add 8% on the SAFC in order to get it 14.7 ish. If I forget it's +8%, and turn the AC on, it does the same thing as you described and the AFR is mid 10's.

 

And it will remain so until a different upper is on Which will be a long ways away. My cam spacers have the intake closing @ 56* abdc though, I believe most are running 44*

 

guys I'm also having the same bogging issue. However I did take it to the dyno just to get some numbers before tuning. it only did 178 whp and stuttering under 4500 rpms. I can post up a sheet if you guys would like to see.

 

Ahh, I was almost to call since we know how well the stock IM flows after 5600. Get a dyno you lazy .org member.

That is what we're all about.. Post up, heck may as well even send me the runfiles.

 

Dyno sheet would be great!

 

Let the mod do his job and myob. I stated what he said and added to it which is done in many of the threads here.

Anyway to other guys w/ 3.5 swap, once we get a raised rev limiter and get on a dyno to get tuned I believe a majority of the problem should b solved. Aarons spacers is supposed to add sum decent low/mid range power also, so after I install it and tune I will b sure to let u guys know about the improvements.

 

I wasn't trying to 'myob' I was pointing out that it has been discussed before and is starting to get

ETA?

 

That is NOT within specification. Spec is ~4V @ WOT. You're almost 1V too high.

 

ok guys here's my graph. don't laugh at my weak sauce power lol

Run one is the original run and run 6 is the final number messing with the afc

 

Jesus That's a whole heck of a lot of area under the curve for just AFC adjustments.

What else was done? ~ 40 ft/lbs in some areas.

 

oh yeah i didnt hook up the butterfly to a vacuum source on the first run but it still put out the same power. i added fuel to the map thats why the a/f's are close to low 13s. my setup up is a 3.5 swap, 6 puck act sprung clutch w/ HD pressure plate, stock header, custom y-pipe, and custom 3in straight exhaust( car used to be supercharged 3.0). still running the 3.0 ecu with the afc hack waiting for EU.

 

Hooking up the power valve to a vacuum source =

You might as well not connect anything to it since there's really no vacuum @ WOT. You need a window switch to operate it properly. In any case, those numbers are SEVERELY anemic. Have you tried doing a compression test? What's your vacuum like @ idle?

 

when i had the valve zip tied open it ran like crap like run 1. when i hooked up the vacuum it ran a whole lot better. in any case, the dyno numbers are pretty embarassing. my vacuum at idle is at -20psi. I'm waiting to do a leak down test on it.

 

Those curves look like meximax's runs when he tested different VIAS settings. http://forums.maxima.org/showthread.php?t=475915

 

The 3.5 power valve is OPEN by default. When you zip-tied it "open" you were actually closing it. That's why there was no top-end power. Attaching a vacuum source to it basically left it open since there no vacuum @ WOT. Hence why it felt better. I suggest just leaving it alone (open) in the meantime until you can find a device that can control it properly.

That sounds like a very good place to start.

 

thanks for the info nismology! i wish i thought to not run vacuum to it when on the dyno.

 

dont be mistaken iam not complaining about my powerband.

look in my sig

and my curve only feels bad between 2500-4500 . from idle to 2500 torque is very good.
and keep in mind i have stock timing ,fuel and rev limit. and i dont care about my powerband now i would care even less if i had a 7500 rev limit and some tuning.

 

ur #'s r definately sick, I say ur one the people that prove the potential of 4.5 gen, Did u do sum weight reduction? I think I would need to do way more than u did to see those times, lol keep up the good work

 

ill tell you this, my race weight was right around 2800 lbs for that day at the track.

so get your race weight around that and you may get times like me

also i may dyno this car toward winter because i wont be racing for AWHILE and i may not race this car ever again.depends if my life allows it

 

i can NOT get mine into spec. and i think thats what is causing my hesitation. Sometimes the car feels like it pulls the PROPER ammount and sometimes its holding back..its not always feeling crappy mid-range. Is it even possible to get the 4th gen TPS exactly within specs on the PF TB? i have mine pushed all the way clockwise to get it as close as i can.