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-   -   iPd T cam slow off the line (https://forums.turbobricks.com/showthread.php?t=356647)

adamdrives 08-31-2020 03:00 AM

iPd T cam slow off the line
 
Hey guys, I put an ipd turbo cam in my 740 over the weekend and am a little puzzled by the results. Before install the car was very zippy from a stop. I had set WG preload to 10 ps, verified by calibrated gauge. With the cam installed, and ignition timing at 12*, the car is comically slow off the line--it feels gutless until 3k or so, when it takes off. It definitely pulls harder on the highway, but is very, very slow off the line, even with brake boosting. I've searched around and experiences seem to vary. I just watched a video of a stock, mbc and T cam equipped 940 spinning through 1st and netting a 6 second 0-60--that would be impossible in my car. Is it normal to lose much low end?

My plan is to make sure the harmonic balancer hasn't slipped and the timing marks are accurate, but it seems odd that power was okay before. I tried advancing the adjustable gear 2 and then 4 degrees, which made no noticeable difference. Valve clearances were all between .014-.018 when I installed the cam. Any ideas?

TurboDutch 08-31-2020 03:55 AM

Oh boy that's bad news

Harlard 08-31-2020 01:13 PM

Sounds like your timing is off indeed. Easiest way to tell if it slipped is by checking base idle timing with a light. If it's not at 12 it is for sure slipped. You will lose some torque at the bottom end but the powerband should be nice and nearly stock smooth.

Also, FWIW, a good approximation for that cam is -4 degrees on a timing gear. That's where it lands when you set it to Enem's (original manufacturer) spec of 1mm of opening at TDC. This should result in more torque through the entire powerband (yes, even at low RPM).

adamdrives 08-31-2020 06:44 PM

I did check with a timing light and the timing is at 12 deg. I’ll make sure the balancer is in the correct position after work. When you say -4 degrees, do you mean btdc, meaning advanced? Thanks

Harlard 08-31-2020 07:41 PM

No, 4 degrees retarded. The cam has too much advance built in.

Usually having the timing light illuminating the harmonic balancer on the wrong spot is the dead giveaway. You could also try erasing the ECU's fuel trims by disconnecting it for an hour and see where that gets you.

gsellstr 08-31-2020 08:15 PM

You sure about those numbers Harald? On my IPD cam, 1mm open required around 1* advanced. Taking into account the head height, I'm running 4* advanced, for an actual of 1* against the crank.

Yeah, it's not as torquey off the line as my VX was, and it doesn't bark on the 1-2 shift like the VX, but it also winds out a lot better, pulls better across the band, and doesn't hit a wall at 5k like the VX did.

OP, assuming LH2.2 car here, since you're talking advancing the timing. 12* should be fine, definitely check cam timing, make sure something didn't slip a tooth.

Harlard 08-31-2020 09:32 PM

Quote:

Originally Posted by gsellstr (Post 6109971)
You sure about those numbers Harald? On my IPD cam, 1mm open required around 1* advanced. Taking into account the head height, I'm running 4* advanced, for an actual of 1* against the crank.

Weird. You sure it wasn't shaved a whole bunch? -4 has been it for a few heads.

adamdrives 09-01-2020 12:10 AM

Well, the balancer had a slipped, but that’s not the issue. Got a known good one on and it’s still a dog off the line. Gear set to 0, timing at 12* btdc. I’ll upload a 0-60 video for a sanity check, but I’m pretty sure it’s around 10 seconds.

gsellstr 09-01-2020 12:30 AM

Quote:

Originally Posted by Harlard (Post 6109976)
Weird. You sure it wasn't shaved a whole bunch? -4 has been it for a few heads.


Yeah, actually did the proper setup on it in the 531, came in at -4 to run straight up, but I know how much that head had been shaved down, comes out to around 3* for that. I'll check the next one as well, when I setup the Ph1 in the SPM head for the next build.

turbotankshane 09-01-2020 01:01 AM

if its an auto car, consider a converter change.

adamdrives 09-01-2020 01:33 AM

Quote:

Originally Posted by turbotankshane (Post 6110013)
if its an auto car, consider a converter change.

The car doesn't like to shift out of first until its warm, so that could be part of the issue, but it seems to shift and hold power fine once warm. Do you mean a straight swap? Or is there a converter that would be better matched.

edit: well, now im wondering if maybe the car loses first when hot. I just watched the 0-60 video I took this morning and it stays in "first" gear until around 45 mph. Anyone know how much mph it should have at the end of first? Looking around for gear ratios now.

edit2: no, looks like 1st should end up around 45mph or so with back of the envelope calculation. Sigh. How to get more low end?

Harlard 09-01-2020 02:45 AM

Did you reset the ECU yet?

VB242 09-01-2020 10:20 AM

Quote:

Originally Posted by adamdrives (Post 6110018)
The car doesn't like to shift out of first until its warm, so that could be part of the issue, but it seems to shift and hold power fine once warm. Do you mean a straight swap? Or is there a converter that would be better matched.

edit: well, now im wondering if maybe the car loses first when hot. I just watched the 0-60 video I took this morning and it stays in "first" gear until around 45 mph. Anyone know how much mph it should have at the end of first? Looking around for gear ratios now.

edit2: no, looks like 1st should end up around 45mph or so with back of the envelope calculation. Sigh. How to get more low end?

You could run smaller diameter tires, which will change your effective gearing.

dbarton 09-01-2020 11:00 AM

Or consider reversing the installation and see if it goes back to its peppy normal.
Dave B.

adamdrives 09-01-2020 12:35 PM

I will reset the ecu today and see if there is any change. If that doesn’t do anything I think I will put in the stock (T?) cam and see how it drives.

Harlard 09-01-2020 12:37 PM

Set it to -4 and reset the ECU. Go.

gsellstr 09-01-2020 01:57 PM

I'm with Harald, give that a shot.

With a 6800 limiter in mine, it'll hit around 40-45 in 1st, around 80-85 in 2nd. The stock converter isn't that poorly matched actually, depending on what turbo you've got. I did find mine responds a world better with an MBC to help boost ramp up faster, even if it's the same boost level as the WG.

shoestring 09-01-2020 03:18 PM

Given the number of these threads of late (2 or 3, maybe 4) where there is a complaint of no low-end torque and a common denominator of a particular cam swap, perhaps we need to ask if there might be something wrong with the grind? I know that one thread in maintenance had issues prior to said cam swap, but who knows if the original concern was fixed and then the cam swap introduced new, similar symptoms?

This all just seems a strange coincidence to me.

adamdrives 09-02-2020 12:17 AM

Left the battery unhooked all day, reset cam gear to -4, if anything the car is slower off the line :/

Gonna find a cheap mbc and see if that “fixes” my issue. It definitely pulls hard once it’s going, maybe it’s just my expectations? We’ll see.

gsellstr 09-02-2020 01:05 AM

Ok, -4...is that retarded or advanced? Some people get them mixed up.

adamdrives 09-02-2020 12:21 PM

Retarded.

FWIW, I've adjusted the gear 4 degrees in both directions with no real change in the huge hole in power below 3k.

DET17 09-02-2020 12:46 PM

How do we know this gent has his balancer reading true TDC for #1 ?

I run the IPD cam and with LH2.4 (spark timing proper) it pulls hard just as soon as the 19t spools, which is NOW. My cam is advanced 4* because shaved head (so probably actually straight up). I have a 4.10 final gear so I have 10% less speed in each gear than Gary listed. My cam was shimmed properly which required the full IPD shim rental kit to achieve. These aftermarket cams never adjust properly with factory shims.

I sense wrong spark and or cam timing. The IPD cam works, period.

cosbySweater 09-02-2020 01:04 PM

What turbo do you have, is your kickdown adjusted right. There are so many variables here. Also if it's a stock frame turbo, be it 13c 15g or whatever just throw a stock t cam in it. The ipd cam is a waste of time with one of those tiny turbos

Harlard 09-02-2020 01:15 PM

Quote:

Originally Posted by DET17 (Post 6110436)
How do we know this gent has his balancer reading true TDC for #1 ?

I run the IPD cam and with LH2.4 (spark timing proper) it pulls hard just as soon as the 19t spools, which is NOW. My cam is advanced 4* because shaved head (so probably actually straight up). I have a 4.10 final gear so I have 10% less speed in each gear than Gary listed. My cam was shimmed properly which required the full IPD shim rental kit to achieve. These aftermarket cams never adjust properly with factory shims.

I sense wrong spark and or cam timing. The IPD cam works, period.

Base ignition advance isn't hardware adjustable. If the balancer slipped, it would be readily noticeable with a timing light, ASSU</a>MING the idle switch on the throttle body is functioning correctly.

OP, check your cam timing again. If you don't trust your balancer, check the mark at the back of the crank timing gear or check piston height with an extension.

My guess is that your cam timing is still a tooth off.

gsellstr 09-02-2020 01:41 PM

Harald...the question still hasn't been answered on what year the car is. 2.2 can adjust base timing. Given the 12* spec, I'm under the ASSumption this is an LH2.2 car.

OP...4* retarded will absolutely make it more of a dog out of the hole, should hit nice around 4k. For now run it around 4* advanced, works reasonably well with the auto trans. As mentioned, it won't have the torque the T cam had, but it shouldn't be a dog either.

Erik brings up a good point on making sure the kickdown cable is adjusted correctly as well. While that won't make your power out of the hole night and day better, it may help get the power to the ground.

I'm with Harald as well, check your cam timing against the washer under the timing cover, make sure it's all lined up right. Being a 740, if the cam timing is off, that also changes your spark timing, so every time you change your cam timing, you'll need to reset your ignition timing as well.


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