Dyno Pull yesterday (OBX Headers)
 

After 2 months of thrashing on the track conversion, I finally got the car to my buddies shop for a track alighnment. While there, we strapped it down for a quick dyno pull to make sure all of the changes worked properly (OBX headers/Plenum coolant elim/Secondary vac elim)
Only had time for one quick pull, but I'm pleased with the numbers! 339.8 HP/342.2 TQ. That's compared to 309 HP/310 TQ in 2003 through the stock manifolds with Flowmaster cat back. The Flowmasters sound even better throught the headers!!!

***EDIT***OOPS.....I just went through all of my files on the car, and the first numbers were through the stock exhaust (NOT THE FLOWMASTER CAT BACK)***

Headed to VIR next weekend for her first event!

Done so far!
Vansteel coilover package
Banski spherical/heim camber rods
Banski spherical/heim toe rods
Banski spherical/heim trailing arm rods
SPC spherical/heim front upper A-arms
Exotic Muscle adjustable sway bar end links
Del-A-Lum lower A-arm bushings
Poly sway bar bushings (w/front relocation block)
DRM camber rod brackets
DRM trailing arm brackets
Carbotech pads
DRM brake bias spring
Nitto NT-01
Hurst short throw shifter
C beam plates
Elite Engineering oil catch can
Block plenum/TB coolant flow
Removed secondary vac, actuators & blades
OBX headers
Removed secodary vac system
Haibeck reprogram for secondaries & headers
DRM Chassis bar
Kirkey seats
Crow harnesses
MOMO steering wheel and adapter (2 ohm resistor for airbag light)

:cheers:

Re: Dyno Pull yesterday (OBX Headers)
 

Very cool!

Love to see some video of that beast in action!

:cheers:

David

Re: Dyno Pull yesterday (OBX Headers)
 

339.8??

Curious... have you done a compression check, and if so, do you remember what it did?

30 is a good bump for headers, but seems there is more to be had at that. Could be the dyno too, I guess. Anybody else? ?

Re: Dyno Pull yesterday (OBX Headers)
 

Wish I could say it was just the headers, but I can't!
2 different Dyno jets.
New injectors last year.

***I just went through all of my files on the car, and the first numbers were through the stock exhaust (NOT THE FLOWMASTER CAT BACK)***

Re: Dyno Pull yesterday (OBX Headers)
 

i believe the difference was compared to a totally stk exhaust . kinda tough to figure the individual improvement with all the changes that were made ,. as dominic shared in an earlier thread , one needs to chassis dyno tune the car to get the most out of ones changes . generic tunes only go so far . jmho . but 30 more hp will stiil be alot of fun

Re: Dyno Pull yesterday (OBX Headers)
 

Road racers should be aware that water pump cavitation occurs at 6100 rpm. Engine speed over 6100 rpm for more than a few seconds can overheat the engine. I know of two LT5’s that have pushed back head gaskets at VIR.

The common scenario is the driver is busy driving and the check engine light goes on because the coolant has reached the 250 degrees F. high temperature limit. The driver becomes aware of the situation when the engine control system disables the secondary port throttles.

If the driver up shifts and runs the engine at less than 5500 rpm, the engine temperature will drop rapidly as the coolant circulation resumes. The engine temperature will usually return to a normal 210 degrees or so in about half of a lap.

The failure mechanism is that the aluminum liners expand much more than the steel head bolts. The gasket gets crushed and then fits loose after the engine cools. Normal driving eventually pushes the loose fitting gasket off the liner at the exhaust coolant passage.

Reducing the pump speed can raise the cavitation speed. A ZR-1 Products under drive water pump pulley will raise the cavitation speed to 6400 rpm. If an under drive water pump pulley is used with an ATI under drive crankshaft pulley the cavitation speed will increase to 7500 rpm. Use of the two pulleys may cause the engine to run hotter at idle with the AC on.

Re: Dyno Pull yesterday (OBX Headers)
 

Marc is there a way to ring the head....and would that help this issue??

Re: Dyno Pull yesterday (OBX Headers)
 

Seems a little odd that the rwTQ is higher than rwhp. Mine put out around 330 rwTQ and about 350hp. That was run in 3rd gear (stock manifolds). I have heard discussions that some cars will show 5-10 hp more if you run in 4th. Then there is the individual dyno and the elevation of the test etc etc.

The one thing that does jive is that headers/exhaust are good for an easy 30 rwhp.

Re: Dyno Pull yesterday (OBX Headers)
 

Nice numbers

Re: Dyno Pull yesterday (OBX Headers)
 

Hi Lee,

The OE gaskets work well up to 650 hp if the engine does not detonate excessively or overheat. A wire ring can help lock the OE gasket in place. However the modern solution is to use a MLS head gasket. It’s easier to install MLS gaskets than to modify the cylinder heads.

The OE gasket crushes to fit. It does not rebound much when the clamping force is increased and then reduced. A MLS gasket will spring back if it is over-clamped on a hot engine. We use MLS head gaskets on all of our assemblies.

Still the fundamental problem of overheating should be addressed directly. Head gaskets are easy to replace compared to other damage that an overheating engine might sustain.

Re: Dyno Pull yesterday (OBX Headers)
 

Thanks Marc! Shouldn't be a problem getting her to short shift for her first couple of track days. She's pretty good at using a shift light vs. having to read the tach. I'll start working on getting a set of pullies installed real soon.

Re: Dyno Pull yesterday (OBX Headers)
 

What group do you run with at VIR? That track is on my list to try sometime. Looks like some great mods!

Re: Dyno Pull yesterday (OBX Headers)
 

I might as well interject a thought. While cavation could be a problem and is a known issue with the LT-5 I would contend that the bypass system is the root of the problem and much easier to solve.Mark is correct that the engine heat generated by rpms over 6100 rises faster than one in a racing environment can contend with, however this is due more to the fact the water ceases to flow through the radiator when the rpms pass 5800 or so rpms. In fact over 5800rpm the water is routed directly back into the block via the bypass which helps explain the dramitic increase in temp.

I do not have the skills to reengineer the bypass but I have tested in normal driving and at least one owner tested in racing the following.

1. Install a radiator that can flow at least 100 gpm.
2. Cut the thermo spring so that it is always open.
3. Block the bypass flow path with a plug.

I ran this configuration for over 50k miles with no overheating, in fact I had to block the radiator with cardboard in winter to have enough heat for the heater. This configuration was what Fastlane used in his car (it was he who told me this trick) and was tested by at least one roadracer with satisfactory results.

Tyler

Re: Dyno Pull yesterday (OBX Headers)
 

I'm all ears! I'll explore all options!!

:happy1:

Re: Dyno Pull yesterday (OBX Headers)
 

Although Im glad to see the increase in hp do to headers and by no means want to burst any bubbles but 309rwhp tells me there's a problem somewhere. At the very least a healthy stock LT5 should put down 325rwhp. Mine put down 340rwhp 335 ft with stock manifolds and just an old Borla. Mine once dynoed at 309 only because my drivers side cat decided to expload and exit the exuast and Corey took his foot off the gas. Corey said it was actually pretty awesome. A big flame shot out the muffler and honeycomb substrait hit the wall. Lol!

Re: Dyno Pull yesterday (OBX Headers)
 

Ok as far as heat - would it not help if the water pump was ported in some way ( to create more flow)? what about using waterwetter ? Are there any part numbers for a higher flow radiator?
I too used to cut the spring (center) out of my thermostats and just use it as a restrictor to help slow the water down a little... it always helped..

Re: Dyno Pull yesterday (OBX Headers)
 

Yep, my 91 was about average, stock with B&B's and some light plenum porting by Aaron in the old days. It did 346 and 337.

This is from Marc's website:

Upgrade: '90-'92

Original equipment engine power 375

Low back pressure exhaust system +10

Performance engine calibration (chip) +10

Subtotal 395
Long Tube Headers +25
Subtotal 420
420x.85=357

So not too far off...

Cheers,
RH

Re: Dyno Pull yesterday (OBX Headers)
 

Shrek,

Asside from a (low?) 309 hp baseline, 30 hp gain seems about right compared to the results others have had for the same mods, as well as what Marc H's web site data suggests. That's a good thing, but it tends to support (in my mind anyway) that the baseline number may be even more indicative of something else that "ain't quaht raht" here.

For example, here is a bone stock 90 (except for a Borla cat-back exhaust) that pulled 339 rwhp - pretty close to what yours makes after headers, etc. THIS is what makes me wonder if there is a gremlin that needs to be rooted out in the base case, as your car responded very much in line with what others experience for the same mods.

Note: On the dyno runs (below) the A/F ratio was getting too lean - turned out the secondary fuel pump was not working - so the operator was cutting it off at around 6k rpm. And, note it was stock except for a Borla cat-back. (The resonator tubes diameter were something like 1-3/4": no resonance, but also "a bit" restrictive too.)

http://i185.photobucket.com/albums/x...20-08Large.jpg

Shrek, I hope you don't think I'm being a "Debby Downer" or throwing cold water on your improvements. It is because the improvement value is typical that it brings attention to the fact the baseline and end results are not what is also typical, and there may be a reason - maybe even a simple fix - for it.

For example, Dom discovered the secondary throttle plates in his TB weren't opening fully when the accellerator was floored. A simple adjustment and voila! Same thing happened on my wife's C3.

I'm just sayin, 20+ hp is 20+ hp. And, hell...guys spend $300-$400 to pick up 5 hp from porting the TB! So, I'll shut up about it now, but I just thought it might be worth a look. Could be dyno error too, for that matter.

Good luck!

P.

PS: I just noticed something... The new torque number is higher than my baseline number, but the hp is not. Is the torque/power curve dropping off suddenly above 6000 rpm or was the run cut off prematurely? Any chance we could see the dyno sheets - before and after??? That might be the answer to this question. If it is, then we'll know.

Re: Dyno Pull yesterday (OBX Headers)
 

Not a problem Paul. There could have easily been a problem with the motor way back then. My guess would be injectors! I was always a little bummed about the 309, because the other two 91's that day pulled high teens and low 20's. But the car always ran smooth and felt like good power for a weekend cruiser for the wife. That was until the injectors caused it to start bucking and missing last year. I put in a set of FIC injectors and could tell right away that we had more power than before but never got it to the dyno to confirm my butt dyno. My guess is we could probably get more power now with a custom tune. It was definitely running a tad rich on this tune from Marc, but since she probably wouldn't notice the difference, I'm going to play it safe and let her have at it like it is.

I'll get a copy of each dyno posted up. :cheers:

***EDIT*** Here are the sheets!

2003
http://i446.photobucket.com/albums/q...Dyno2-1-03.jpg


2012
http://i446.photobucket.com/albums/q...yno2-11-12.jpg

Re: Dyno Pull yesterday (OBX Headers)
 

She's going to run with the NASA group first, then we'll branch out to some other clubs. Even though she has many, many laps on track with the NCCC, we're going to start her off in group one until she learns to play nice with other cars on the track.

Re: Dyno Pull yesterday (OBX Headers)
 

Let us know how it goes. Have fun!

Re: Dyno Pull yesterday (OBX Headers)
 

Added dyno sheets to post #19 :cheers:

Re: Dyno Pull yesterday (OBX Headers)
 

Ah, Ha! I kinda suspected that! There's more gold in that thar LT5.

For comparison, a selection of curves I have on file; one (my first one = stock/Borla) and the rest = various mods. Ingnoring the numbers, it is the characteristic shape of the torque/power curves vs. rpm that I am trying to illustrate for comparision. See whatcha think...

My stock w/Borla (only)

http://i185.photobucket.com/albums/x...20-08Large.jpg

Two for one: Don's and Dominic's after P&P, and Dom's with headers too maybe??

http://i185.photobucket.com/albums/x...noCompar1A.jpg

A 415 creation by Marc...

http://i185.photobucket.com/albums/x...motiveTech.jpg

A 350, fully ported, stock cams and headers/3" exhaust...

http://i185.photobucket.com/albums/x...T510-19-10.jpg

And now, if I may draw your attention to your torque vs. power curve...

2012
http://i446.photobucket.com/albums/q...yno2-11-12.jpg[/QUOTE]

The torque curve is falling off too soon. I kinda thought from that stock 309 hp figure that there must be some more oomph hiding in there. Looks like there should be another 25-30 to be had if the reason for the torque collapsing could be addressed?? Something. (Cam timing crossed my mind first; is why I asked about compression check results. If one side was significantly different by comparision, it could be that "something".)

Spark? Cam timing? Who knows. I can analyze data and graphs with the best of 'em. But, for some real expertise, maybe Marc or Pete can shed some light on it. Something like 20-30 hp more to look forward to!

P.

Re: Dyno Pull yesterday (OBX Headers)
 

Thanks Paul! "When" it starts to drop off doesn't look to be too bad! It's the linear dive vs. the gradual curve down as seen on the other graphs that concerns me.



Here's a graph from my buddies stock 93 with Power Effects.

1st pull...key off & power effects open...HP-238.49 TQ-308.21
2nd pull...key on & power effects open...HP-360.81 TQ-332.90
3rd pull...key on & power effects closed...HP-346.94 TQ-332.07

http://i446.photobucket.com/albums/q...1/DSCN0654.jpg

Re: Dyno Pull yesterday (OBX Headers)
 

Stock LT5's should be peaking around 5900 rpm...maybe a couple of hundred rpm higher for the 405hp cars.

I would not get too carried away with wondering how the cams are timed etc until you check the fundamentals. You should be able to pull to 6000, especially with headers. Is your intake boot collapsing?

Looks like you have plenty of fuel up high..like too much, I would have expected 12.5 AFR from the factory VE table.

ON Edit: extrapolating that curve should put you at at least 350+ whp

Re: Dyno Pull yesterday (OBX Headers)
 

Best of Luck on the track. Wish I were there to see her get back in the Road Course Saddle with other cars on track. At least she is not going to have to deal the the famous "Kink" and add a third Red, Red '91 ZR-1 to the loop de loop group Brooke and I started!

Re: Dyno Pull yesterday (OBX Headers)
 

Any updates on issues possible for low rwhp vs conservative dyno?