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Discussion Starter · #1 ·
Since raising revs on a production engine far beyond its production limit is usually extremely expensive and fraught with all sorts of hidden problems to solve - I was considering a potential increase in displacement as a plan B if 2GR power didn't quite "do it" in the long term.

Keep in mind this is just a thought experiment - interested to hear other's thoughts on it.

Ultimate goal is to get a reasonable stroke/displacement increase that still works with ~7-7.4k RPM using stock pistons and a projected stroking price of ~$1-1.5k. The easiest way to do this is via offset grinding the crank and using an off the shelf rod that can be made to work.


2GR-FE stock specs (in mm): bore 94, stroke 83, rod length 147.5, rod big Dia 56, rod big width 20.83, rod small dia 22, rod small width 20.83.

Using an H22A aftermarket rod, you'd have: bore 94, stroke 92, rod length 143 (this drives a 4.5 mm * 2 = 9 mm stroke increase), rod big Dia 51, rod big W 23.75, rod small dia 22, rod small width 23.875

Bolded items that changed.

You'd have to get the crank offset ground 4.5 mm to the outside, but you have 5 mm total diameter change to work with, so that leaves 0.5 mm to cleanup on the outer edge to ensure everything is completely concentric and in profile. The big and small end of the rod will need to be milled down ~3 mm, but the small end diameter is the same. Assuming a fairly low mileage 2GR, you can likely take out the factory pistons and do a quick rehone after checking the bores and slap in some new rings after checking ring gaps. New bearings and gaskets all around since you're taking stuff apart, but that shouldn't be a huge amount. Final displacement would go up to 3831 cc, a 375 cc (~10.8%) increase over stock. Rod/stroke ratio goes from 1.78 to 1.55 - which is getting more aggressive, but should be fine for a ~7.4k RPM max engine.

The outer webbing of the block to rod clearance should be good since the outer edge of the rod should remain in about the same spot. The higher pressure loading on the big end bearing should be fine for the revs that are being run, even with a relatively heavy stock piston.

The only potential issue I see is the piston skirt potentially coming in contact with the crank counterweight and/or pulling out of the bores slightly. The bottom of the piston will extend down the bore an extra 9 mm, and be an extra 9 mm closer to the crank counterweight. Maybe the piston skirts would need some slight notching and balancing across all 6 to fix that.


I'm less familiar with offset V6 crank balancing, but I imagine the crank would also need balancing after the offset grinding and rod weight loss. Crank hardening required after? Although for an engine that's not going to see 200k+ miles of usage, it might not be so important since it's more the start/stop of the crank that benefits from the harder journals.



Just a high level concept, but I don't see any obvious show stoppers. With some mild cams, it should easily push out over 300 rwhp and get a nice big torque bump all across the rev range.


Thoughts?
 

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I'm not opposed to this concept by any means but if your goal is just to run a mild cam and rev it to say 8000 RPM and put down 300-320 to the ground you can do that without cracking the engine open just replacing the valve springs. I've done that on my car and the rockers have not flown out neither has the oil pressure gone to ____ nor has there been any rod damage. Car is running great after more than one year of constant abuse. I do have a spare block sitting here awaiting the day that cash and time become available for a stroker. I would be more ambitious with that maybe to the tune of 500bhp on a 3.9-liter bore at 10000RPM with ITB's but that is just me dreaming out loud.
 

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With the increase in stroke and the shorter rod, you are increasing the piston acceleration by more than 10%. I wouldn't assume that you can run these rods and pistons up to the same redline as the OE engine.
 

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Discussion Starter · #4 ·
With the increase in stroke and the shorter rod, you are increasing the piston acceleration by more than 10%. I wouldn't assume that you can run these rods and pistons up to the same redline as the OE engine.
Yes, the peak acceleration is higher probably on the order of 15-20% vs. the OE configuration. But the OE configuration is VERY low stressed as far as modern bottom ends go. A 92 mm stroke with a 1.55 rod/stroke ratio is perfectly happy at 7.2-7.4k RPM all day long assuming the parts have structural capacity. The piston, wrist pin, aftermarket rods, and crank (even with the reduced journal overlap) should all be good to go. Will it live 300k mi if you beat the snot out of it at 7.4k RPM like the OE configuration? Maybe not, but I'd bet it'll still be running fine when the rest of the car is falling apart.

This isn't that far off an F22C1 Honda engine (2.2L S2000) with a ~91 mm stroke and ~1.6x rod/stroke ratio and 8.2k RPM redline stock. People routinely bump that up to 8.6k RPM and they live forever like that. So hanging out in the mid 7k RPM range isn't going to cause a problem IMO.



So with just valve springs and some regrind cams the stock bottom end is perfectly happy at 8k RPM? That's actually good to know. Nissan non-HR VQ35's do not like over 7.2k RPM, and tend to blow the oil pump up when revved higher. I don't see why you couldn't take the poor man's stroker motor to 8k RPM if you're willing to live with a potential failure at some point - that IMO, isn't extremely likely given the rods are going to be much stronger than stock. 350 rwhp possible?


Over 350-360 rwhp doesn't seem very likely on stock head ports, no matter what is bolted to the engine.
 

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Discussion Starter · #5 ·
BTW - Compression ratio would go up to around 12.0:1 with this change and stock pistons, which would be a perfect limit for a premium pump gas NA engine. No more 87 octane though...



Also, if you went to some 96 mm VQ35DE pistons with sleeves (per Ray Hall Turbocharging -), you'd get ~4L of displacement. That said, no idea if the compression height is the same between a VQ35DE piston and a 2GR-FE piston. The wrist pin is the same diameter, and same small end width I think.

But at that point, you're talking big money to resleeve a block, and IMO, it usually causes problems in the long run with sunken sleeves, or water leaks etc. I'd keep things cheaper and do the poor man's stroker well before sleeving the block. Especially since 92 mm stroke and a 1.55 rod/stroke ratio is still capable of enough revs to max the stock head out.
 

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Over 350-360 rwhp doesn't seem very likely on stock head ports, no matter what is bolted to the engine.
I'm not sure why you're saying that. there's a ton of Exige guys with completely unopened motors making more than that. And if you think they are running some special heads here's a dyno run 12hp from that range that i did by bolting on the TRD supercharger with stock pulley to a 100% stock 2008 highlander motor using the factory TRD ECU with just a bit of timing tweaks on it:


For reference the stock TRD lower intake manifold is absolutely terrible. it was designed to fit in a stock camry and that involved a ton of airflow sacrifices.
 

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Discussion Starter · #7 ·
Well obviously I wasn't talking about FI - 300 rwhp NA head ports are not a restriction at say 400 rwhp and a higher total intake pressure.

NA power is largely limited by the total head flow, and you can optimize things with bolt-ons then cams to get the highest volumetric efficiency in the rev range that things can work in. But if the head can't flow it, that's it.
 

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Well obviously I wasn't talking about FI - 300 rwhp NA head ports are not a restriction at say 400 rwhp and a higher total intake pressure.
sorry, with this part of the statement i did not realize you were talking about NA only:

DefSport said:
no matter what is bolted to the engine.
What you're talking is about 400-420hp at the flywheel, let's say 410hp to have a single number to talk about. That's 119hp/L of displacement with the stock displacement. That is certainly in the range of things that are achievable but yeah it's right at the outer reaches. if we stay with reasonable VE numbers making that kind of power from an NA setup generally takes about 8500-9000RPM and it's safe to say that the heads on a toyota camry are not designed to be efficient 40% higher than their redline.

Also, your original numbers above are faulty, when you offset grind a crank you have to grind away 1mm of material for every 1mm in extra stroke. you double the difference but when offset grinding you only gain half the distance ground. so to gain 9mm you'd have to offset grind 9mm bringing the rod journal diameter down below 47mm. since this is an even fire engine the conrod journals offset and much of the strength comes from the overlap between the journals. reducing the diameter here can make a dramatic strength change.

The stock crank has a rod journal overlap area of 374mm^2, your proposed stroker setup has a rod journal overlap that is 2mm^2. Granted, this crank does have balance plates between paired cylinders so the crank can still physically be made but it will be weaker for sure.

If you wanted to stroke the 2GR on a budget i'd start with a 1GR-FE crankshaft. it has a 95mm stroke to begin with so it will displace 4.0L. of course it isn't that easy though. the conrod journal diameter on the 1gr is the same 56mm as the 2gr and you don't have to grind it down but that's where the nice stuff ends. the 1GR has much larger main bearings of 72mm so they would have to be machined down to the 61mm required by the 2gr block.

the next issue is the rear main bearing is a different diameter. unfortunately you can't just cut this down because the bolt pattern for the 1gr-fe crank would interfere with the oil seal diameter on the 2gr-fe. so you do have to use the larger rear main on the 2gr. thankfully this main is pressed into a plate that is bolted on. the 1gr plate has a different pattern than the 2gr so you'd need a custom one but this is a relatively cheap part to get made at a local machine shop. you only need to get them to hit it +/- 0.5mm which is a really loose tolerance on an engine. of course the closer it is the longer that rear main will last.

You'll also need to either modify the crank or the flywheel to make them mate together. another reasonable operation for a local machine shop and i'd recommend machining the flywheel and not the crank.

The next issue is the rod length. the 1gr rod is about 160mm. this does not give us an exact deck height but it does tell us that the 1gr's deck is likely 15-20mm taller than the 2gr so we can't just use the 1gr rods and pistons in the 2gr block. you can likely hunt and find an off the shelf part for one or the other and then only have to get custom pistons or custom rods to keep the cost down.

but this quickly avalanches to something that is no longer worthy of the "budget" phrase used to start this thread.
 

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What is the limiting factor of airflow with the 2gr heads? Is it port size, valve size, or what? I know it's a totally different engine/manufacturer and even displacement but I recently looked into a low mile 370Z. While looking into possible bolt on mods I of course watched some dyno videos. A VQ37 with headers, exhaust, intake, ported upper intake manifold, and a tune those engines make just over 400hp and just over 300 lb/ft. These are flywheels ratings of course, not whp. WIth Jim Wolf Technology stage 1 exhaust cams peak numbers rise a bit but the mid range picks up something like 25 lb/ft. Anyway, I initially thought that these engines would have been pretty close in stats but obviously not. Nissan VQ35s seem to make pretty healthy power with bolt-ons too.
 

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I'm not opposed to this concept by any means but if your goal is just to run a mild cam and rev it to say 8000 RPM and put down 300-320 to the ground you can do that without cracking the engine open just replacing the valve springs. I've done that on my car and the rockers have not flown out neither has the oil pressure gone to ____ nor has there been any rod damage. Car is running great after more than one year of constant abuse. I do have a spare block sitting here awaiting the day that cash and time become available for a stroker. I would be more ambitious with that maybe to the tune of 500bhp on a 3.9-liter bore at 10000RPM with ITB's but that is just me dreaming out loud.
Strongly agree with what he said. If you want 300-320whp. Just do valve springs and MWR regrind cams.
 

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Discussion Starter · #11 ·
Gouky, you're right, I missed that in my original spreadsheet with the rod journal centerline only changing by half the amount ground off. That means these rods would not work, as you'd need some that were a couple mm longer.

Maybe ~3.7L is possible with the rod rods, but I didn't see any that would work on quick review. Will look more over the next couple of days.


As for the power, sure 300-320 rwhp is doable with mild cams and zinging things up more, but a bit more displacement will likely make more power with mild cams and give more torque everywhere.
 

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Discussion Starter · #12 ·
What is the limiting factor of airflow with the 2gr heads? Is it port size, valve size, or what? I know it's a totally different engine/manufacturer and even displacement but I recently looked into a low mile 370Z. While looking into possible bolt on mods I of course watched some dyno videos. A VQ37 with headers, exhaust, intake, ported upper intake manifold, and a tune those engines make just over 400hp and just over 300 lb/ft. These are flywheels ratings of course, not whp. WIth Jim Wolf Technology stage 1 exhaust cams peak numbers rise a bit but the mid range picks up something like 25 lb/ft. Anyway, I initially thought that these engines would have been pretty close in stats but obviously not. Nissan VQ35s seem to make pretty healthy power with bolt-ons too.
It's more the port shape than anything else, although valve size etc. does play a role. The VQ37VHR heads have very large intake ports, and a HUGE intake cam at max duration/lift. It's on the order of ~290-300 degrees total duration and ~13 mm of lift, so it can really take advantage of that big intake port.

The VQ37 is an evolution of the VQ35HR heads, which flow quite a bit more than the earlier VQ35DE heads.

Here's some good info:

https://www.onpointdyno.com/vq35-hr-vs-de-head-flow/


A VQ35DE with cams and bolt-ons will struggle to crack about 265-275 rwhp (the rear diff and driveshaft add to drivetrain losses, would be more like 280-285 rwhp in an MR2 transaxle type layout). While a VQ35HR with the same bolt-ons, and higher flowing heads can easily put out over 300 rwhp. Heck, an HR can do 270 rwhp STOCK, which is what a really tarted up DE will do, and bolt-ons will usually put them right below 300 rwhp.

The HR has higher flowing heads and a bottom end that will let it rev up an extra 500 RPM to take advantage of it.
 

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Since there's nobody here but us chicken, here's something else to throw into the mix. For some time now I've been fascinated with these ITB's for the VQ35:

https://www.ebay.com/itm/OBX-Indivi...231972307605?_trksid=p2385738.m4383.l4275.c10



My idea is to take this $1,500 kit, and discard the cross-over runners, and the fuel rails, and mount the throttle bodies and velocity stacks straight down onto the stock lower manifold. This would require an adapter plate of some kind, either plastic or aluminum.



Pros of doing this: relatively cheap, easy to install, keeps the fuel rail and injectors accessible.

Cons: requires re-installing the stock gas pedal and cable, requires most likely a tps load-based tune, most likely does not fit under engine lid, some solution needed for a vacuum reservoir for brake, pcv, evap vsv.... nothing really insurmountable.

Now for some other questions:

- What do we think this would net for added HP or TQ? I've seen estimates of 30HP.

- How's the drivability on something like this? My year-round constant climate does not require any active idle control... But is this a streetable setup? Has anyone driven something like this?

- How do we tune runner length? This would be achieved with the adapter plate, either thinner or thicker...

- Any other thoughts about pros and cons versus the stock intake plenum?

- I'm approaching this as a bolt-on... without any other head/engine work. Does it even make sense to do this?

Any thoughts or suggestions appreciated.

PS. It would be cool if I could find just one of these throttle bodies to play around with and test fit onto my spare manifold - anybody know where to get one? They must be made by... someone? Quick look at summit racing yields nothing comparable.

PPS. So it turns out that the OBX throttle bodies are junk. However I did find references to alternatives, like for example Hayabusa GSX1300 TBs, same diameter (48mm), better quality, or even 4AGE [blacktop] 20V throttle bodies, also 48mm...

PPPS. With more digging I found the ITB kit that probably served as the "inspiration" for the OBX knockoff. Nearly twice the price.

https://foxinjection.com/collection...-sf-taper-throttle-body-kit-with-curved-horns

These folks also sell a simpler ITB kit for the Ford Duratec V6. It seems like a better candidate for adapting to our manifold.

https://foxinjection.com/collection...oducts/ford-v6-duratec-sf45-throttle-body-kit
 

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It's more the port shape than anything else, although valve size etc. does play a role. The VQ37VHR heads have very large intake ports, and a HUGE intake cam at max duration/lift. It's on the order of ~290-300 degrees total duration and ~13 mm of lift, so it can really take advantage of that big intake port.

The VQ37 is an evolution of the VQ35HR heads, which flow quite a bit more than the earlier VQ35DE heads.

Here's some good info:

https://www.onpointdyno.com/vq35-hr-vs-de-head-flow/


A VQ35DE with cams and bolt-ons will struggle to crack about 265-275 rwhp (the rear diff and driveshaft add to drivetrain losses, would be more like 280-285 rwhp in an MR2 transaxle type layout). While a VQ35HR with the same bolt-ons, and higher flowing heads can easily put out over 300 rwhp. Heck, an HR can do 270 rwhp STOCK, which is what a really tarted up DE will do, and bolt-ons will usually put them right below 300 rwhp.

The HR has higher flowing heads and a bottom end that will let it rev up an extra 500 RPM to take advantage of it.
Makes sense. The VQ37 does have variable lift on the intake cams. From what I've read you really don't have to touch the intakes cams unless you are going high boost or really high hp naturally. Healthy gains in the exhaust cams though like I mentioned. Just looked at the port flow graphs. The ported DE head barely outflows the stock HR head and only at max valve lift. Damn.

Is here enough meat on 2GR heads to be able to open them up and reshape them? Is there enough room to use large enough valves to make the higher hp numbers?
 

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Discussion Starter · #15 ·
Did some more digging, looks like Honda F20B (JDM only engine I think) rods work. 145 mm rod length, which gives an 88 mm stroke vs. 83 mm stock stroke. Rod big end dia is down to 48 mm, and crank rod journal dia goes from 53 mm stock to 45 mm. Lots of meat to regrind only a 2.5 mm centerline change, but less journal overlap. I wouldn't think bearing pressure would be problematic at our RPM, but I dunno, a 2GR piston weighs a lot more than the 85 mm bore F20B piston. Final displacement would be 3664 cc, so only a small bump. Based on that, probably not worth doing unless you were looking at getting that final bit out of the engine.



As for ITBs, they're good for some things, but I wouldn't say they make power by themselves. You still have to tune the runner length and volume. Plus you're definitely talking about a standalone at that point to get it to all work together. You can definitely get an engine to idle without an IACV, I've done it before. But you can also get a simple PWM 2 wire IACV to work with ITBs. You just plumb the IACV into a common plenum for each runner. Doesn't need a big line to provide enough idle air.

I'm not sure the ITB thing really makes a ton of sense. I'd personally just fab up a nice intake manifold like this with a big single TB:

I guess you could toss ITBs on something like that as well, but then you have to make a plenum for the ITBs if you want to run a filter, which is a pain, standalone etc.

With a fabbed single TB plenum you could run the stock ECU, maybe find a way to get a larger TB on it etc. Wouldn't be into it a huge amount if you can do some basic fab work.
 

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The stock throttle body seems pretty huge already. I don't know for sure, but it seems like it wouldn't be a restriction for quit a while... I wonder what kind of power gains are possible with an optimized intake manifold though.
 

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The stock manifold barely has any vacuum at all when at wide open throttle at peak hp so the throttle body isn't much of a restriction. The intake runners are quite long which makes better torque down low, shortening them may help peak horsepower at the cost of torque down low but the lightweight MR2 can handle a bit less torque down low.

From what I understand the major restriction on this motor is the exhaust ports and it's cam lift/duration.
 

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Discussion Starter · #18 ·
The stock throttle body seems pretty huge already. I don't know for sure, but it seems like it wouldn't be a restriction for quit a while... I wonder what kind of power gains are possible with an optimized intake manifold though.
You don't need much vacuum to take a lot quite a lot of NA power.

Isn't it just a 70 mm TB? That's not very large for a ~350 BHP engine. VQ35DEs made more power as they stepped up in TB area, with the last Maxima engines have the VQ35HR heads and a 75 mm TB.

There's probably not a ton of power there as with all NA mods, but NA is all about chasing small gains that all add up.
 

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It's closer to 75mm ID I think. I haven't measured the ID, but a 3" coupler is a pretty tough fit on the outside of the throttle body. I think it measures 80mm or a little more on the outside, so probably close to 75mm ID.
 

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Discussion Starter · #20 ·
75 mm ID is probably good enough, but there's always the chance of unlocking some more power there. Especially once cams are added to help the breathing out. ...or if someone is a glutton for ~200 cc more capacity and they choose to do some budget stroker action. :)
 
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