LS4 build

[ericjon262]

Thanks for the Aluminum block info!

I'll try and weigh my bare cradle some time this next week and let you know for sure what it weighs.

[The Dark Side of Will]

I have an entire 88 suspension currently.
What I'm after is reduced weight, and altered geometry to correct for a lowered car, like raising the inner pivots.
This cradle would end up at about 35lbs welded with 1.75" OD .125" wall primary steel tubing. without mounts.

Making something out of aluminum I can see the weight being 25lbs (with larger tubing to increase rigidity)

If I recall, the Factory 88 Cradle weighs near 60lbs bare.

The inner pivot for the forward lateral link on the driver's side is under the edge of the inner CV joint. In order to move up an inch, it has to move forward about half an inch to clear the CV joint. Of course the transmission is immediately inboard of the CV joint.

The structure you show there around the inner pivots will interfere with... everything.

[FieroWanaBe1]

The inner pivot for the forward lateral link on the driver's side is under the edge of the inner CV joint. In order to move up an inch, it has to move forward about half an inch to clear the CV joint. Of course the transmission is immediately inboard of the CV joint.

The structure you show there around the inner pivots will interfere with... everything.

I started taking my idea of a tubular cradle and comparing it to the factory cradle. I have been working on putting a engine and transmission model into the assembly too. Things already have begun to be moved around. I know its probably too close to the driveline on the drivers side as it was modeled up.

[FieroWanaBe1]

Thanks for the Aluminum block info!

I'll try and weigh my bare cradle some time this next week and let you know for sure what it weighs.

https://youtu.be/mSKNwvBI9rY?si=PFQlU90k43upeeHk

People have bored a LS4 to 3.898" bores. In my opinion the Jury is out on weather the motor is suitable for such a large bore. People have re-sleeved LS1 blocks and they ran for a short while, but the consensus is that the sleeves will crack eventually.

[FieroWanaBe1]

I asked about the machining done on that LS4 video. LS4King commented that they have been able to open up the factory sleeves to 4.00". Curious, I emailed him asking for more information because that doesn't seem possible on my block, but I also have never seen a cross section of the LS4 block to know for sure.

I also grabbed some better measuring tools out of my toolbox to check my engine, I previously had only used a tire depth gauge to measure the bore thickness in mm, and rounded down. This didn't accommodate the curvature of the cylinder very well clearly.

This time I used a telescoping gauge and a true dial caliper, as well as a digital inside caliper to measure the aluminum below the sleeve. My Dial bore gauge doesn't fit there because the wheels are to large for just the aluminum portion.
I measured a maximum of 3.91 on the inside caliper (this tool is only accurate to the nearest .01", I bought it for head porting) and the telescoping gauge with the dial caliper measuring the gauge, measures at 3.907. The actual cylinder bore measured 3.778. I think its in the ballpark.

If the sleeve resembles an LS1 sleeve, there are only two answers I can think of:

My block is a 2006, maybe there is different versions of the block with different liner geometries, similar to 24X or 58X.

Or the sleeve is deeper than the bare aluminum at the bottom of the bore.

Or they cannot be opened up past the .010" over bore.

[FieroWanaBe1]

Screenshot 2023-08-28 083339.jpg (72.55 KiB) Viewed 3593 times

Screenshot 2023-08-28 081542.jpg (152.68 KiB) Viewed 3593 times

The scaling isn't great, plus I cant be sure how to scale these drawings are.
But interference may be less than initial assumptions.

[ericjon262]

if I remember, I'll try and snap a couple of pictures of how close my F23 is to the lateral links, there's not much room at all.

[FieroWanaBe1]

Since all my effort towards this is theoretical and constant war gaming at the moment:

More information about the LS4 GenIII vs GENIV block oddities:
This is the LS6 Block (Definitely a GenIII) and a a 5.3 Gen III, all the aluminum blocks have this appearance behind the timing cover.

Screenshot 2023-08-30 081644.jpg (191.22 KiB) Viewed 3552 times

This is a GenIV 5.3 Block, A LS2 Block, and a LS7 Block. All Gen IV blocks have this appearance behind the timing cover.

Screenshot 2023-08-30 081918.jpg (142.48 KiB) Viewed 3552 times

This is my LS4 block.

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the LS4 clearly has the Gen IV DoD valley, and knock sensor location, but under timing cover its looks like GenIII tooling.

[ericjon262]

sorry, pictures are crap, if I have a wheel off any time soon I'll try and snap a better one.





I'm fairly certain Fieroguru took similar pictures with an F40, and it had significantly less clearance.

[FieroWanaBe1]

It appears there is only enough room for around 1" rise on the pivots, I would also ditch to square socket like shape of the mounting point and use just two tabs, to maximize vertical clearance.

[FieroWanaBe1]

IMG_8168.jpg (45.43 KiB) Viewed 3526 times

This is the photo if found from FieroGuru with the F40,
I think, he kept the factory engine crankshaft centerline, therefor the F40 moves the axle centerline forward in the vehicle.
It looks like the fore pivot has less clearance to his CV joint, which is I think is different than the Fiero cup somehow.

Raising the pivot with this configuration would be more difficult.
I am curious how much more compact a 930 or 934 CV could be if at all.

[Emc209i]

What I'm after is reduced weight, and altered geometry to correct for a lowered car, like raising the inner pivots.
If I recall, the Factory 88 Cradle weighs near 60lbs bare.

Ah ok. Yeah the stock cradle is heafty, but I always thought this a plus given what it does. I've bottomed my cradle out a lot in 20 years, happy to have a heavy piece of steel down there.

You're building a race car. I just wanna drive mine on Friday nights. Carry on.

[FieroWanaBe1]

What I'm after is reduced weight, and altered geometry to correct for a lowered car, like raising the inner pivots.
If I recall, the Factory 88 Cradle weighs near 60lbs bare.

Ah ok. Yeah the stock cradle is heafty, but I always thought this a plus given what it does. I've bottomed my cradle out a lot in 20 years, happy to have a heavy piece of steel down there.

You're building a race car. I just wanna drive mine on Friday nights. Carry on.

I'm not saying I plan to sell a bunch of cradles to people, but the possibility is out there.

but, if a viable design can be produced for an 88 type suspension replacement for non 88 owners, that has a slight bit better geometry than the beloved 1988, and can use stronger wheel bearings, it may be usable for a few people who can't find all the necessary hardware to use on a pre-88 car.

[The Dark Side of Will]

I'm not saying I plan to sell a bunch of cradles to people, but the possibility is out there.

but, if a viable design can be produced for an 88 type suspension replacement for non 88 owners, that has a slight bit better geometry than the beloved 1988, and can use stronger wheel bearings, it may be usable for a few people who can't find all the necessary hardware to use on a pre-88 car.

I've been thinking similarly... I think I can build a cradle from self-fixturing laser or water jet cut plates effectively

[Shaun41178(2)]

Fiero guru built his own new lower cradle and if I recall, there was some weight saving but not as much as I think should have been considering the amount of time it took to build.

[FieroWanaBe1]

Fiero guru built his own new lower cradle and if I recall, there was some weight saving but not as much as I think should have been considering the amount of time it took to build.

So right now it is 21.8 lbs lighter, but will continue to get heavier. If I can end up with the cradle 15 lbs lighter, that would be awesome! Here is the tubular cradle in its current state. I still need to weld the mount tabs, add the lateral and trailing link suspension tabs, and add a few gusset tubes

[FieroWanaBe1]

I have been reconsidering my Water pump scheme, read below:
LS Coolant Flow:

LS cooling system - numbered.jpg (89.97 KiB) Viewed 3436 times

I currently have on my shelf the Meziere remote mechanical pump: WP430S

Meziere makes a coolant manifold, WAM119S https://www.summitracing.com/parts/mez- ... ?rrec=true

Unless FieroGuru releases his own manifold with t-stat sooner, I may try to order one, but I will still need to use my remote T-state housing (Moroso 63425). This makes plumbing very complex, as I need to fashion a heater bypass) and the -12 ports may be too small.

I also have this: https://www.amazon.com/gp/product/B0BF1 ... UTF8&psc=1 and it may package better.

I also have a couple of sets of water pump spacers, to see if I can try to use a modified LS4 water pump setup with the LS3 crank pulley I have. I would love to figure out what the LS4 pump flows. I should try to test one someday.

Meziere flow graph:

Screenshot 2023-09-06 111417.jpg (30.49 KiB) Viewed 3436 times

Pierberg:

Screenshot 2023-09-06 120058.jpg (79.14 KiB) Viewed 3436 times

Now onto my cooling system Math:

50/50 Volume Ethylene Glycol Water Mix Specific Gravity @ 180F = 1.044

50/50 Mass Ethylene Glycol Water Mix Specific Heat @ 180F = .873 BTU/lb F

Assume 50/50 mass = 50/50 volume (Horseshoes and Hand Grenades)

Radiator Top Tank Temperature = (Thermostat Open temp + 20F) This is arbitrary ( air speed, rad size, core type, flow dependent variable)

Thermostat Temp = 160F
Top Tank Temp = 180F
Flow Rate = 55 GPM (max rating of Meziere’s Remote Electrical Pump and the mechanical at 4000RPM (The large Pierburg 7.03665.66.0 is 70L/Min or 18.5 GPM)

Heat Flux = (180F-160F)*0.873BTU/lb-F * 8.1LB/GAL * 1.044 = 8147 BTU/MIN = 192HP

How is this useful?
Two Criteria I can think of, what would the average power level be at a Track? My goal would be to take this car for a track weekend at Road America, Gingerman, or Autobahn Country Club. I don’t have data logs to use, but If there is an average power during a lap to be derived from such, we could determine what the total heat removed from the engine needs to be over time.

Second, As a rule of thumb: 1/3 of all chemical power from an engine goes to torque production, 1/3 to exhaust heat, and 1/3 to water jacket heat. Starting here we can begin sizing components when engine specific data is not known. A 400 HP engine Auto engine generally doesn’t spend all day making 400HP, especially cruising. Ideally, we have a pump control, to tailor the coolant flow to the cooling power required. That can either be a ratio of engine speed (such as an engine driven pump), an electronic pump controller, such as a PWM pump unit like BMW has been using, or just the thermostat alone, and rely on the thermostat to open and close flow to the radiator alone (SBC installs).

That is where the average power around a track may be helpful. With sufficient cooling capacity, we can absorb the 400HP when necessary and during dwell time under deceleration where engine power is very small cool the coolant to lower than operating temperatures. This works so long as the average system flow rate can cool above the average power level. This is why so many people say Electric pumps lack the flow for high performance driving outside of drag racing, they can’t flow enough for sustained power absorption outside of the drag racing duty cycle.
A more efficient radiator, be it better airflow, or a more efficient core, can improve this but we are limited to airspeed and ambient temp conditions. A 100% efficient radiator can only cool our theoretical engine from Ambient up to the maximum top tank temp, (this is the designer’s choice, and you need to base it of a criterion such as Air to Boil Temp, when Air to Boil is reached the coolant boils, and cooling performance disappears entirely).

So lets assume a summertime 85F ambient (ignoring humidity effects)
T air in = 85, T air out max = 180F (top tank temp from before)
Cp of air at 85F = .240 BTU/LB-F
Density of Air at 85F = 0.0728 lb/ft^3
Dh= 0.240 BTU/LB-F * (180F-85F) * 0.0728 lb/ft^3 = 1.67 BTU/ft^3
Radiator Area = 19.75” x 15” = 296 sq-in = 2.057 sq-ft
Air Speed 55MPH (Co Hwy or corner exit) = 4840 ft/min
Airflow = 4840 ft/min *2.057 ft^2 = 9956 ft^3/min
Heat Flux = Dh*Q = 1.67 BTU/ft^3*9956 ft^3/min = 16627 BTU/min = 392HP
That’s the maximum possible (not achievable) power absorption at traffic speeds, the capacity lowers at lower speeds, and raises at higher speeds.
We have also ignored aerodynamic effects and Turbulence, as well as radiant cooling.

Air to Boil = (BP – (Tcool in – Tair in)
Air to Boil =(225F –(180F – 85F)=130F, so probably safe for extreme hot days.

Anyways, I have yet to convince myself to run an electrical Water pump like the Peirberg unit. I will have to look at what the average power of a lap at road America could look like based on positive acceleration data vs time of similar enough car of a known weight.

Edited for clarity

[FieroWanaBe1]

I remembered,
I own a G-Tech RR.
I pulled a data log from my old LS1 GTO during a track day:
I multiplied velocity by forward g's and again by 3800lb to get approx. instantaneous power (negating incline and aero drag)

Screenshot 2023-09-07 171141.jpg (40.63 KiB) Viewed 3414 times

Physics 100 math:
Force [lb]=mass[slug]*accel [ft/s^s] or Force [lb] =Weight [lb]*g (mass [slug] = Weight [lb]/ 32.2 [ft/s^2] 1 g = 32.2 ft/s^2)
velocity [ft/s] =distance [ft]/ time [s]
work =Force [lb] * distance [ft]
work =Weight [lb]*g*distance [ft]
Power [ft-lb/s]=work [lb-ft] /time [s]
Power=Weight [lb]*g*distance [ft] /time [s]
P=Weight [lb]*g*velocity [ft/s] / 550 [ft-lb/s per HP]

in the CSV I made this fantasy HP unitless by dividing by the rated 350.
Excel reported average of .23

so the engine average power was ROUGHLY around 25%.

Basic Thermo-1 math makes the needed flow for adequate cooling at 25% of my goal: 35GPM to cool 122HP with a 20 degree radiator delta.

Edit to add:
I had excel use 15hp if forward acceleration at any point was less than 0, to remove the effect of braking on heat, Since I don't know the effect of engine braking on engine heat.

[Series8217]

A bare 88 cradle weighs 53 lbs.

[FieroWanaBe1]

A bare 88 cradle weighs 53 lbs.

Thank You, that confirms other data I have seen. I think there can be something of similar stiffness made with a loss of mass here.