On the dyno in the am

[BR3W CITY]

Originally Posted by hotrod 80

I know im gonna get hit for this one , but the turbo 400 is heavy and is a poer hog .

Steam is piping out of my ears and I'm about to explode like a cartoon character from this statement.

Keep your glide, just put a G/V behind it.

[Super73]

When I went from the 80e to a glide, I toyed with the th400 idea. But... 2 well known and respected trans shops told me the same thing. At my weight (then 3,525) the two transmissions would net out the same. The th400 would provide a better 60' but the glide would net more mph and it would be pretty much a wash, this is providing the correct converter was used.

Being I knew I would be shaving more weight, they both pointed me towards a glide for consistency.

Keep in mind, I am not trying for a max effort NA combo, but I am trying to find the best balance between what will be +/-400rwhp hit worth of n20 and NA. I know there will be some sacrifices.. Definitely in the NA set up where I won't be riding the verter and the shift extension is dropping me >2k rpm. But testing on the small hit is telling me this is not a factor then, I am riding the verter at that point.

The glide is a 1.76 gear.

[BigDan3131]

If you buy the "right TH400" you will have what you want and then some. Try Mike's Transmissions at http://www.mikestransmission.com/index.html I would either give them a call or email them. They were building the best stuff when everyone else were still trying to use factory parts.

[Super73]

Dan,

Both Mike's and abruzzi told me to go glide. I went with abruzzi and their service has been awesome.

[Marv D]

Just something to think about,,, I've ran across a few heavy hitter N2o guys here in Az using modded TH400's as a poor mans glide. (using the 1.48 / 1.00 gears of launching in 2nd gear) I'm no nitrous guy but the instant hit of 800-1000# of instant torque can be serious traction problem. The 1.48 gear and the right converter can soften the hit to the tire.

Just wondering if you have ever tried a manual 2nd gear launch. Hell I've done it plenty of times by accident,,, it slowed my 60' down about a tenth,, (cause I was way underpowered for so much gear) but ET and MPH was almost the same as POUNDING on the tire with a 1st gear launch.

Where that's coming form...
I do know a guy here with a big inch BBC nitrous motor that is all in to this street outlaw crap. In Tucson at 6000+ da summer races,, he uses 1st gear and runs high 8's
Comes to Phx in the good air (2000' da) when the tracks tight he launches in 2nd and steps up the timers for more hit earlier in the run. Said he does the same on the street,, just launches in 2nd to help keep it hooked.

Different strokes... You got your trans ordered so kind of a moot point,,,just food for thought.

[PGSigns]

Just my thoughts but until you get the weight split a little better and get some good shocks it will be hard to tune. Is you convertor built for all on nitrous or NA? Putting the wheel tubs and bed sheet metal in it and the tailgate will improve the balance. Double adjustable front and rear shocks will allow you to fix a lot of the problems you are having. Have you done a 4 link map for you setup?
Jimmy

[Super73]

4-link is 54 out and 6 3/4 off the ground.
Rear shocks are double adjustable Koni's

I don't disagree that having a better balance is overall a good thing. With the old spring it would theoretically lift the front faster and make the issue even worse. But then the argument of the added weight on the rear tire might keep it planted. Who knows really with out actual testing.

We will see what happens next weekend with the old cam and stiffer front spring in it.


I was comparing the Brian Tooley cam I have not tried against my "old cam" that is now back in the motor. Some thoughts for those of you that like the analytical part of this game as much as I do.


My old cam is a 254/260 109icl 111lsa
The BTR cam is a 251/266 108icl 112lsa

On the surface the BTR looks to be more of a N20 friendly cam, larger split and wider LSA. But let’s dig deeper.

Installed dot to dot (no advance/retard added via timing set), the BTR cam would have the same IVC and EVO as my old cam if it were installed on a 107icl. While the same is true if the BTR cam was installed on a 112icl and my old cam was installed dot to dot 111icl.


Old on a 107icl vs BTR on a 108icl
IVC 54* vs 53.5* ABDC
EVO 69* BBDC for both

Old on 111icl vs BTR on a 112icl
IVC 58* vs 57.5* ABDC
EVO 65* BBDC for both

The difference is really in the EVC and IVO naturally affecting the overlap. Yes the BTR cam technically has 6* more exhaust duration to aid in cleaning out the cyl, but I have some thoughts on that, I will get to it in a bit.

Before I go there, I seem to remember Vizard explaining in his book that a power adder such as N20 does not require the same amount of overlap as an NA motor and also gains from opening the exhaust valve earlier as it helps to reduce pumping losses. Obviously spreading the LSA covers both of those provided duration both intake and exhaust stay constant.

To the Vizard point of reducing or not needing the overlap with N20; In conversations with John Dougherty, Tony Mamo, Brian Tooley and some online discussions with a few other seemingly intelligent people, there is an argument that you don’t need the overlap a NA motor requires because you are feeding the motor good clean oxygen and not relying on the exhaust to kick start the flow. This could also play to your thought that N20 could extend the RPM range as you are providing the motor with more breath, makes sense to me.

I have also heard that too much overlap and you could be in fact be allowing the N20 to go out the exhaust valve. I am going to come back around on this too in a moment.


On to the difference between my old cam and the BTR cam regarding IVO, EVC and overlap.

Where do these cams put the overlap? Is it biased towards BTDC or ATDC?

First I am going to assume the BTR cam is on the 108icl it is ground on and compare it to my old cam on a 107icl.

Old = IVO 20* BTDC - EVC 11* ATDC = 31* overlap and it is biased towards BTDC by 9*
BTR = IVO 17.5* BTDC - EVC 17* ATDC = 34.5* overlap and it is biased towards BTDC by 0.5*

Here are thoughts and questions I have:
At this point does the additional 6* of exhaust duration really help the BTR cam?
It is on the tail end of the exhaust cylce, how much exhaust gas is left to clean out?
Could N20 escape with the added overlap?
If a N20 motor does not require the overlap wouldn’t my old cam be favored from that stand point?
How does the 9* of BTDC overlap bias my old cam has play in here? At low RPM it might create reversion toying with drivability, but at high RPM is it going to really matter?

[BR3W CITY]

[PGSigns]

The shock is going to do more to control the speed of the front. On the motor I think you are going to need a shorter instant center and for both setups loosen up the rebound on the shock to hit the tire a little harder.
Jimmy

[GMR-PERFORMANCE]

I am going to swap over to a custom ground cam by bullet that Straub will spec for me. Its not free meaning he gets money to design the cam. TOO many guys have gone very fast with his custom specs for it to be a fluke.

I am happy with what I have but I know there is more in what I have.. I refuse to give up the 4L80E.. SUper and I have had this talk a few times.

Chassis dyno needs to be done in top gear without a lock up TC that wil be what it is.

I feel that a Chassis dyno is great to get you 95% tuned. ITs a WOT pull in top gear.. Take the info for what it shows and tune from there.