Endurance racing turbos

Being completely ignorant concerning boosting a car that never had boost, I'm hoping some here will feel free to pass some knowledge.

Hypothetical-Freshly rebuilt longblock 350 small block Chevy, max rpm 5500 with around 10-12 pounds of boost with an intercooler. Compression around 8.5 to 9:1 with smallish valves. Either a Holley Sniper with throttle body or a Terminator X controlling factory TPI to have better control to avoid detonation. Want to avoid a blow through carb setup.

In my internet research I have found a fair number of examples of guys driving on the street and drag racing setups like this but nothing for endurance/road racing. Crank horsepower desired 380-420hp. Torque should not be an issue at all from what I have found.

Beyond fuel injection, I am thinking a remote mount may be good for heat management and keeping the area under the hood from becoming so cluttered it makes cooling difficult. A slight power loss, if there is one, would be a good tradeoff to keep the heat down.

The thinking behind this is in Champcar a turbo system, including headers/intake/wastegates/blowoff's/etc is 100 points with the intercooler being an additonal 25. To make the same power traditionally with heads, cam, valve springs, headers, intake, throttle body/carb would be well over 200 points. Heads alone are 100 points. One could get away without the replacement heads but that would require a much more radical cam, and higher rpm, with related reliability issues.

Thoughts on a low boost, low rpm build surviving 14 hours in a weekend?

Do you have enough fuel to support that hp?  That is about twice the horsepower the vast majority of champcar have.

As for the setup?  I never had good luck endurance racing sbc. Had head gasket issues, spun bearings, etc, etc, etc...

#sendit!

Thousands of SBC's are wailed on, at far higher rpm, every weekend at circle tracks around the country. With stock rods and cast cranks. Not concerned about the long block as long as detonation is avoided. Note I said a rebuild. Not a junkyard pullout that has been fuel washed every day for 20 years before sitting idle for 15 more.

23-26 gallons is enough to feed that horsepower and not be taking more pitstops than the front runners. At the big tracks none of the cars on the pointy end can make 2 hours.

BigIron said:

Thousands of SBC's are wailed on, at far higher rpm, every weekend at circle tracks around the country. With stock rods and cast cranks. Not concerned about the long block as long as detonation is avoided. Note I said a rebuild. Not a junkyard pullout that has been fuel washed every day for 20 years before sitting idle for 15 more.

 

23-26 gallons is enough to feed that horsepower and not be taking more pitstops than the front runners. At the big tracks none of the cars on the pointy end can make 2 hours.

SBC's at the cheaper end of the Endurance racing world historically have not held up well.

pure built race engines can, obviously, but the average one just won't do that.  Running at WOT for nearly 12 hours is quite different than an evening's worth of sprint races.

Adding boost is burning the candle at both ends of the stick after you've cut that stick in half.

invest heavily in cooling, not just big radiators and oil coolers, but controlling the oil and ensuring the proper parts are cooled effectively.  Ducting after the radiator and in the engine bay is also important to consider and manage.

Let's not forget the fastest, and multiple race winning, car in Champcar last year was SBC powered.

Not concerned about the long block as long as temps, rpm, and detonation are controlled. It will be a "new" engine, completely rebuilt with proper tolerances for racing and good fasteners/parts. Not Chinesium rockers and such.

Does the remote mounting of the turbo sound like a good plan? That is mostly due to cooling. Also concerned about packaging both a large intercooler and radiator. Perhaps the intercooler could be mounted somewhere besides the typical in front of rad location and the remote mount may help that.

edit-I went back an re-read my OP and I need to clarify. I specified the engine size, could be either a 305 or 350, as I have no idea on what size turbo(s?) one would run to maintain good throttle response. No need for them to build more than 12-15 pounds of boost, but they need to flow enough air so it doesn't nose over at 5k and reducing backpressure should reduce heat as I understand.

 At the big tracks none of the cars on the pointy end can make 2 hours.

That's not quite true.  I can only think of 2 tracks were that may be true. Road America and Daytona. 

Plenty of cars at the pointy end go 2 hours.

As for the GBU corvette....  (built by Riley)  w elll, let's just say it's value was interestingly adjusted due to creative help from a certain tech person who no longer is associated with Champcar.  It did get 15 laps of points added to it....

The winning car in champcar to date is a turbo car.  It is a saab!

You're looking at doing an old school low-tech turbo build, so I'd look into what old school low-tech endurance racing turbo engines did.  Lots of cooling INSIDE the engine: rich mixtures, remarkably low compression.  A lot of those old turbo engines would run so rich that the exhaust was barely visible and had compression in the 6:1-7:1 range.

No this isn't the way to make big power, but do you want to make power for 12 seconds or 12 hours?

I'd also seriously look into the coolant rerouting strategies people do to make SBCs live for even 20 minute races when at higher power levels naturally aspirated.  The exhaust valves/seats at 3&5 and 4&6 are one of the places that SBCs are really weak, and turbocharging will give you even more problems there.

To Pete's point a lot of these strategies are important because of uneven fuel/air distribution. This is not much helped by TBI and only a little better with untrimmed port injection. To get things to survive, rich enough to keep the leanest cylinder alive is important. It's WAY different on an endurance car, you have to have reasonable goals and what may seem like way too much cooling system. 

I help with tuning a Champ VW and we make maybe 150whp out of the little 2L and have to keep it there to have it live on a relatively stock engine. I can easily crack 300whp on one of these in a street setup without issue due to the lower heat load and duty cycle.

In reply to BigIron :

It won't work 

  Not because of the turbo but because of oiling.   The Chevy small block is wonderful for street driving or even drag racing. 
But road racing. That's different because of corners and stopping.  You have to do those as aggressively as possible in order to be competitive. 
  When you do the hot oil slides up the side or into the timing chain area. instead of staying around the pickup. 
   As a result no oil around the pick up.  
  It might be a second or so maybe a little longer in a long corner.   
But that time is enough to starve the bearings when the load is highest. 
Champ car gives a 100 point penalty for a dry sump and only a 10 point penalty for an accusump.  One works and one doesn't.   You might live on a 60 second autocross with an accusump  but not for 7 hours racing. And definitely not for 24 hours. 
    I tried every band aide approach I could, yes accusump.  Once I gave up and bought a dry sump my engine lasted for decades. Previously it was pull the engine and replace bearings after every event. ( and those were short 30 minute sessions) 

There are plenty of used chevy small block dry sump systems.   They sell for less than 1/2 of what a new one does. 
     

Naturally aspirated TBI fuel distribution is bad enough - turbo TBI builds tend to make me wince when used for the street or drag racing, and for an endurance race the only way I could see making one work is if you spend a ton of time playing with individual injector trims (Note: I am pretty certain the Sniper does not have individual injector trims) and cutting groves and building fuel dams in the manifold - the sort of things NASCAR teams did before EFI. The only reason to do such a thing is to give a complete middle finger to common sense and put way more work into the build than you would have done with sequential port EFI.

The main thing here is to tune the cylinder trims very precisely - if your ECU allows it, add in a feature that lets you ramp in extra fuel the longer you stay in boost. (This is in the MS3 - I don't know if you can do this with Holley or not.) And I'd go intercooled and take the penalty.  Put the radiator in the trunk  if you've got to  - remember how those old school turbo road race cars Pete mentioned were set up?

If you switch to a different type of fueling, you need to pay the points for that as well.

In a heavy car (3000 lbs), you only need about 250 hp to be competitive. 

Lighter cars,  like a miata, are doing quite well with around 160 hp.

There is a miata with a 1.8 that has the 2nd fastest lap around Road America in Champcar. (Like a 2:43 or something ridiculous like that - this is with running the chicane, and not the kink).

You might want to attend a race or two to see what it takes to be competitive in grassroots endurance racing. Turbo SBC's aren't it. 

wvumtnbkr said:

 At the big tracks none of the cars on the pointy end can make 2 hours.

As for the GBU corvette....  (built by Riley)  w elll, let's just say it's value was interestingly adjusted due to creative help from a certain tech person who no longer is associated with Champcar.  It did get 15 laps of points added to it....

150 points for the rear suspension, that gained it relatively little. Certainly not enough to equal the points hit. It will be about as fast with the stock, mildly improved, suspension or frankly a solid axle. There was no issue with the SBC under the hood and it got no points for said engine.

MadScientistMatt said:

Naturally aspirated TBI fuel distribution is bad enough - turbo TBI builds tend to make me wince when used for the street or drag racing, and for an endurance race the only way I could see making one work is if you spend a ton of time playing with individual injector trims (Note: I am pretty certain the Sniper does not have individual injector trims) and cutting groves and building fuel dams in the manifold - the sort of things NASCAR teams did before EFI. The only reason to do such a thing is to give a complete middle finger to common sense and put way more work into the build than you would have done with sequential port EFI.

The main thing here is to tune the cylinder trims very precisely - if your ECU allows it, add in a feature that lets you ramp in extra fuel the longer you stay in boost. (This is in the MS3 - I don't know if you can do this with Holley or not.) And I'd go intercooled and take the penalty.  Put the radiator in the trunk  if you've got to  - remember how those old school turbo road race cars Pete mentioned were set up?

I'm not seeing how to quote multiple posts, but this, and the posts by Pete and Paul are stuff I am looking for.

The Holley Terminator X can do sequential I believe. If not one of their other systems can so that is covered. The Sniper being a TBI is out.

The Holley systems can be set to add fuel, pull timing, etc based on a number of parameters so using them to make it live is the reasoning behind going that way versus a blow through carb. I know there is no way one could make that setup live for 12 hours short of running pig rich and even then might be dicey.

Regarding the old school turbos, this is why I feel a low boost setup should be able to work. Porsche made what, 1400hp back in '72 with a 5 liter and no computer? 

Some good info and food for thought here.

wvumtnbkr said:

If you switch to a different type of fueling, you need to pay the points for that as well.

 

In a heavy car (3000 lbs), you only need about 250 hp to be competitive. 

25 points for throttle body. ECU is free.

There are no competitive 3000 pound, 250hp cars in Champcar. Unless you are talking wheel horsepower.

My 380-420 numbers are flywheel horsepower, not wheel.

edit-The point is SBC's, as proven by Riley and others, will run fine as long as prepped properly. THe hate thrown upon them is comical. Mostly due to people trying to run worn out, fuel washed junkyard motors and predictably blowing them up. Riley ran an SBC in the Camaro before the Vette and I don't recall it ever blowing up either. It had other issues besides the engine. Years ago the guy with Corvette Racing ran one at Road America as well with zero issues and others run in Champ and other series today. Including 305's.

Point is, don't bring worn out junk and they last just fine as long as you cool and oil them.

What chassis is this going into?

Well yeah, sort of....

There aren't many 3000 lb cars in champcar that are competitive.

There are certainly cars with less hp and less weight (proportianlly) that are competitive.

That's a 12:1 hp to weight ratio.  

In other words, you are better off starting with a lighter car (especially since champcar is basically fuel limited) and have less (and WAY more reliable) HP and go faster (will corner better with less weight).

I'm not saying not to do it, but it just seems the wrong application for a turbocharged sbc.

It would be awesome to see and hear this monster on track!

My car is 12.7:1 and competitive. 

The sc300 are probably 2600# and have 225 hp.  That's 11.5:1.

BigIron said:

wvumtnbkr said:

If you switch to a different type of fueling, you need to pay the points for that as well.

 

In a heavy car (3000 lbs), you only need about 250 hp to be competitive. 

25 points for throttle body. ECU is free.

There are no competitive 3000 pound, 250hp cars in Champcar. Unless you are talking wheel horsepower.

My 380-420 numbers are flywheel horsepower, not wheel.

 

edit-The point is SBC's, as proven by Riley and others, will run fine as long as prepped properly. THe hate thrown upon them is comical. Mostly due to people trying to run worn out, fuel washed junkyard motors and predictably blowing them up. Riley ran an SBC in the Camaro before the Vette and I don't recall it ever blowing up either. It had other issues besides the engine. Years ago the guy with Corvette Racing ran one at Road America as well with zero issues and others run in Champ and other series today. Including 305's.

Point is, don't bring worn out junk and they last just fine as long as you cool and oil them.

 

 

 

Yep....  also, once i ditched the sbc, we have won a bunch of races with our not touched junkyard v6.

To each their own.  You are choosing a difficult path.

Not ragging on the SBC, it just requires a full, and careful build to last.  Not my cup of tea.

Pete. (l33t FS) said:

You're looking at doing an old school low-tech turbo build, so I'd look into what old school low-tech endurance racing turbo engines did.  Lots of cooling INSIDE the engine: rich mixtures, remarkably low compression.  A lot of those old turbo engines would run so rich that the exhaust was barely visible and had compression in the 6:1-7:1 range.

Wanted to come back to this as it raised another question; E85?

I know a lot of turbo guys use it not only to run extra boost but also because it burns cooler. Don't turn up the boost and it may be a big help keeping the combustion chambers happy.

The downside is one will burn at least 25% more of it. I'd have to run the numbers but unless one has a Vette with 26 gallons that definitely wouldn't be workable. Short of running insanely fast laps to make up at least one extra fuel stop.

ross2004 said:

What chassis is this going into?

Looking at either a second gen F body, 23 gallons with cell, or C3 Vette with 26 gallon cell.

The reasoning behind the turbo questions is these cars with 70's smog motors don't have much power stock so it takes a lot of points to get them up to speed under the hood.

I would go for the gas. We would burn around 12 gallons an hour with an NA 350 in a 3rd gen F-body. 

Speaking from experience, the worst part of endurance racing a turbo setup is chasing all of the new little things that are going to break due to the extreme heat from da boost. You can solve almost them all with copious amounts of money in the form of brand new parts.

For example, failures we've had include the manifold to turbo studs fatiguing, the turbo to downpipe studs, and couplers on the intercooler setup failing.   And of course heat management, but you know about that.

The biggest problems all came after a red flag or double yellow situation, so you're racing competitvely for 30 minutes or so, have a whole lotta heat in the system, and then a red/double yellow comes out and things start to cool down.  Green Green Green!!  The race is back on!   AAnnnnnnd, 3 laps later, you've lost your brake master cylinder since the turbo separated from the manifold and is just blowing flame directly on it...

tl;dr:  All inconel studs, all the time.   The best source for 'em is Flyin' Miata.

Having built a turbo Miata and tracked it pretty aggressively for several years, this seems like a bad idea to me.  The recipe for turbo Miatas is pretty well known at this point and even with these advantages I was constantly breaking things or having heat issues.  I was only running around 200whp @ 12psi and the fuel consumption was unbelievable, even with a good professional tune on a modern ECU.  The OP is going to have a janky tune that needs to be pig rich and use even MORE fuel, and the potential issues with heat and mechanical failure haven't been identified yet.

Just put a K-series in a BRZ or Miata and have fun with way less headaches. 

In reply to BigIron :

Porsche made 1200hp with five liters, twelve cylinders (more cylinders per liter), port injection, extremely low compression, extremely large (laggy!) turbine housings for minimal thermal stress, and many MANY man-hours of R&D by a company whose primary occupation was an engineering firm.  I know they did give up on air cooling and went to liquid cooled cylinder heads, cannot remember if this was the 917 engine or if that was the 935.

Just because there is no computer does not mean it is not sophisticated.  IIRC they were using a rather complex mechanical fuel injection, and of course they had a small army of people to engineer and calibrate it.

Part of why they dominated Can-Am was because Can-Am was mostly people on a shoestring budget.