Mainly a cat question but Turbo included for project.

[MrTrendizzle]

Hey so i might've sourced a second IS250 that's in a bit of a state for pretty cheap and i thought i'd have a bit of fun either destroying before the scrap heap or using for scientific research.  

First question: I know i can remove the first two cat's leaving the main cats under the car and pass the MOT just fine. My question is can i join the two pipes together and run a single cat rather than both of them side by side? (See picture 1)  

Second question: Would it be possible to cram a single turbo in the front of the engine (See picture 2) and run the ever so crazy 5psi with very little work (Little piping and a much larger headache obviously) Included in the picture to make it even more complicated a complete cat bypass for track use only. Just ignore that bit. It can be a later stage addon.  

I know this forum hates mods but as i might have a very broken IS250 coming my way i thought i would have a little fun saving my current IS250 from seeing any tracktime. It's way to nice to break having fun in.

EDIT: Queue the hate comments 🙂 Relax i won't be harming my personal car for a bit of fun and sourcing second hand parts from eBay with my own dodgy welding brought to me by Lidl's welder work out at like £300

[Texas]

Just curious on how ‘very broken’ this 250 is? I guess they never ran it dry of oil or you would not be thinking of engine mods. Bodywork? 

[Linas.P]

In theory you only need a single cat in the car, so yes you can remove upper-cats and join pipes into single cat. I assume you want this as it would make easier to do pipe management considering you will have single turbo with single outlet. However, you can't use the standard IS250 cat because it is designed to be used in pair and for relatively low flow (as there are 4 of them to handle everything). So first of all with single cat it would not pass MOT due to emissions, secondly you will burn that single cat, tertiary it will not flow. So what you need is to put single large high flow ("performance") cat in place of one of secondary cats. But if you planning to use it on the track, then why bother with cats? Just straight pipe-it from beginning to the end.

Regarding the second point - this forum does not hate mods. Lexus and IS250 in particular hates mods. Have you seen the engine bay? It is so tight you lose your knuckles just looking at it, working on it is painful and where exactly you planning to fit the turbo? Heat management will be bi*** as well, as you starting to realise you exhaust solution will be difficult as well. And that is just beginning of the issues. 4GR-FSE as most of modern engine have low friction rings, they can't handle forced induction (it will blow by and you just going to cook it), so you will need at very least rebuild the engine and add new rings... which you will have to adapt from some other car, because to surprise of nobody there are no aftermarket parts for 4GR-FSE. Now you have your engine rebuilt at the cost of say £1000 (if you do it yourself). Next step actually fitting the turbo and all the fabrication, add another £1000 (if you do it yourself). Once that is done you need standalone ECU, only the part itself is £1500 to handle DI and 6 cylinders and few more nice things like wideband etc. then you will need to tune it. Can you do it yourself? Else it will be another £1000 considering the hire of dyno etc. And here is the key point why these things are not being done to IS250 (and it is not that people here hate mods) - after spending £4500 you may have 300hp if you lucky, but likely unreliable, not road legal and uninsurable car. Even swapping the engine will be cheaper and more beneficial than turboing 4GR-FSE. So add the price of your project car and suddenly you can just buy another 100 different car for similar price and with more power and more suitable for the track use.

I mean sure, you can just bolt on some old diesel turbo, put scaffolding around it and just wing it - but that will be less of "scientific research" and more of bonfire, you won't make any power at all without ECU and blow the engine before you can even get to the track.

And that is before we even consider all other mods which you may want to do before taking IS250 on track. Answer - just get something else. And this is not because I am trying to save IS250 from being "modified", but because it does not make economical sense for you. 

Just as example of car which will cost less than your mods and will be better for track in itself: https://www.ebay.co.uk/itm/195294356803 or https://www.ebay.co.uk/itm/265821350422

 

[MrTrendizzle]

9 hours ago, Texas said:

Just curious on how ‘very broken’ this 250 is? I guess they never ran it dry of oil or you would not be thinking of engine mods. Bodywork? 

The bodywork is not very attractive. Looks like someone really had a vendetta against the owner. Also the engine looks terrible. No covers, rubber is all cracked and looks like it requires a ton of new hose and inlet pipe. But it runs so a little plastic for the windows and some eBay genuine silicone "flexible" pipes with a £10 cone filter should get it somewhat running. Honestly the car is ready for the scrap heap but for a few hundred quid i thought it would be a fun little experience to see what exactly the 4GR-FSE can handle on the track. If it blows atleast i have a few spare parts to keep in the shed.

5 hours ago, Linas.P said:

In theory you only need a single cat in the car, so yes you can remove upper-cats and join pipes into single cat. I assume you want this as it would make easier to do pipe management considering you will have single turbo with single outlet. However, you can't use the standard IS250 cat because it is designed to be used in pair and for relatively low flow (as there are 4 of them to handle everything). So first of all with single cat it would not pass MOT due to emissions, secondly you will burn that single cat, tertiary it will not flow. So what you need is to put single large high flow ("performance") cat in place of one of secondary cats. But if you planning to use it on the track, then why bother with cats? Just straight pipe-it from beginning to the end.

Regarding the second point - this forum does not hate mods. Lexus and IS250 in particular hates mods. Have you seen the engine bay? It is so tight you lose your knuckles just looking at it, working on it is painful and where exactly you planning to fit the turbo? Heat management will be bi*** as well, as you starting to realise you exhaust solution will be difficult as well. And that is just beginning of the issues. 4GR-FSE as most of modern engine have low friction rings, they can't handle forced induction (it will blow by and you just going to cook it), so you will need at very least rebuild the engine and add new rings... which you will have to adapt from some other car, because to surprise of nobody there are no aftermarket parts for 4GR-FSE. Now you have your engine rebuilt at the cost of say £1000 (if you do it yourself). Next step actually fitting the turbo and all the fabrication, add another £1000 (if you do it yourself). Once that is done you need standalone ECU, only the part itself is £1500 to handle DI and 6 cylinders and few more nice things like wideband etc. then you will need to tune it. Can you do it yourself? Else it will be another £1000 considering the hire of dyno etc. And here is the key point why these things are not being done to IS250 (and it is not that people here hate mods) - after spending £4500 you may have 300hp if you lucky, but likely unreliable, not road legal and uninsurable car. Even swapping the engine will be cheaper and more beneficial than turboing 4GR-FSE. So add the price of your project car and suddenly you can just buy another 100 different car for similar price and with more power and more suitable for the track use.

I mean sure, you can just bolt on some old diesel turbo, put scaffolding around it and just wing it - but that will be less of "scientific research" and more of bonfire, you won't make any power at all without ECU and blow the engine before you can even get to the track.

And that is before we even consider all other mods which you may want to do before taking IS250 on track. Answer - just get something else. And this is not because I am trying to save IS250 from being "modified", but because it does not make economical sense for you. 

Just as example of car which will cost less than your mods and will be better for track in itself: https://www.ebay.co.uk/itm/195294356803 or https://www.ebay.co.uk/itm/265821350422

 

Thank you for the advise. I was trying to keep the exhaust as stock as possible to save as much on piping as i could. Also single pipe would make it much easier rather than trying to split it back for the cats. I did think about MOT just incase i needed to move it on the road for any reason. Better safe than sorry.
I was looking at other threads that explain how the 4GR-FSE is a 12/1 compression with weird ports making it hard to Turbo then i thought hey if the car is for the scrap how bad can double stacking a few head gaskets really be before everything gets shoved out the side of the engine.  

Tune and fuel pump from my understanding the standard ECU, fuel pump and injectors would be absolutely fine with such a low power turbo. Anything beyond 5psi will require more advanced setups. Arma Supercharger runs on the stock ECU from my understanding.  

Tuning - I was going to have a bash at it. Never tried but hey worst case i blow it up, best case i get to blow it up on the track with a smile on my face.  

Turbo location. In my head i was looking at rotating the radiator so it sat at an angle similar to an RX8 allowing a little room for the turbo to sit up front. Obviously heat management would be an issue and to be honest i've not even looked in to that yet. I just fancied like you said a bonfire of bolting a turbo somewhere and seeing what happens. 

Altho now you mention the 350Z dropping a VQ35DE engine in does sound pretty fun if i create an adapter for the stock gearbox. and only costs £1500.

[Linas.P]

Supercarger is another story (none of the issues with heat and piping) and to be honest what they achieving is like 260-280hp, for $7000 it is a bit of the joke, hence they long time closed the shop (or at least stopped making IS250 kits).

I doubt head gasket will be your issue, unless you mean double-stacking to reduce the compression ratio. But I am sure you will blow the piston rings before anything else. Fuel pump and injectors should be fine, but stock ECU won't give you any power... actually I would not be surprised if you get less power after slapping the turbo onto it. Because hot air will detonate, ECU will think "OMG" and retard timing all the way.

You can realistically fit the turbo on the bottom of right hand side, but I haver no idea how you redirect the left bank exhaust manifold there, other option is to fit it instead of airbox and around that area, but the same issue applies - you need very long exhaust extension.

Why engine swap the car with VQ35 and have all the headaches associated with that, if you can simple but the car with the engine already inside for £3000? I just can't see how engine swapping would be cheaper or better?!

[Mr Vlad]

Hi MrT. Look on the American Lexus forum. A few years ago someone fitted twin turbos to their is250. From memory the turbos were located at the rear of the car and the forced air back to the front. It was a very intense build which took quite some months and various trips to specialists. The car ran very well and he sold it about a year later. I think I found the article c/o googling turbo is250. 

If you've got it in your head to do it then best of luck. Don't be put off by it or by anyone. Do find that article as it's a ruddy good one.

[MrTrendizzle]

1 hour ago, Mr Vlad said:

Hi MrT. Look on the American Lexus forum. A few years ago someone fitted twin turbos to their is250. From memory the turbos were located at the rear of the car and the forced air back to the front. It was a very intense build which took quite some months and various trips to specialists. The car ran very well and he sold it about a year later. I think I found the article c/o googling turbo is250. 

If you've got it in your head to do it then best of luck. Don't be put off by it or by anyone. Do find that article as it's a ruddy good one.

Thank you for the tip. I'm not so much as put off, more questioning the cost.  

Car = £500  

Turbo = £160 - £500 (Depending if you want intercooler and pipes etc... Could be cheaper if you get a small used diesel turbo) 

Piping for exhaust = £Free + Headache  

Welding = £Free + Headache and a metric ton of grinding disks to make it look nice  

Relocating radiator to a 45* angle = £Free with headaches and maybe a couple of L shaped brackets.  

Tune = £Free (I'm going to take a stab at it myself with trusty Youtube for help.  

The plan would be to just get it running on 0psi - 5psi to avoid blowing the engine up. and seeing what it can do.  If i can't adjust the AFR or timing on the stock ECU then sure the added cost of a £300 piggyback will have to be factored in but surely for under £800 (Minus car) getting a turbo to run could offer a decent power boost, considering a full stainless exhaust system might net you a few BHP for the same cost.  

Ideally i would much rather pick up another RX8 as my toy but when another IS250 comes along for only a few hundred i can't really say no for parts alone.

[H3XME]

On 8/26/2022 at 11:05 PM, MrTrendizzle said:

Hey so i might've sourced a second IS250 that's in a bit of a state for pretty cheap and i thought i'd have a bit of fun either destroying before the scrap heap or using for scientific research.  

First question: I know i can remove the first two cat's leaving the main cats under the car and pass the MOT just fine. My question is can i join the two pipes together and run a single cat rather than both of them side by side? (See picture 1)  

Second question: Would it be possible to cram a single turbo in the front of the engine (See picture 2) and run the ever so crazy 5psi with very little work (Little piping and a much larger headache obviously) Included in the picture to make it even more complicated a complete cat bypass for track use only. Just ignore that bit. It can be a later stage addon.  

I know this forum hates mods but as i might have a very broken IS250 coming my way i thought i would have a little fun saving my current IS250 from seeing any tracktime. It's way to nice to break having fun in.

EDIT: Queue the hate comments 🙂 Relax i won't be harming my personal car for a bit of fun and sourcing second hand parts from Ebay with my own dodgy welding brought to me by Lidl's welder work out at like £300

Look, if you're going to go through hoops to turbo this car, I wouldn't worry about stupid cats. The 2 secondary cats you can remove and still pass the MOT. Now, if you're going to turbo it, you might just about get away with no cats because it won't be so bad on emissions. Worst case scenario, take it to a modified friendly MOT garage.. nobody will ever suspect it's catless because catless turbo cars are a lot quieter than catless N/A cars.

I think the only issue you'll run into is reliability & space. High compression engines don't like boost and you'll be bending rods or more. I would definitely be up for seeing this or even helping you out as I see you're from the midlands too.. could be an interesting experiment but the lack of people that done this across the pond makes me think it's not something quite worth doing, but then again why bother turboing this when they can have IS350 OR a supercharger from RR Racing. 

[Linas.P]

2 hours ago, H3XME said:

IS350 OR a supercharger from RR Racing. 

Well supercharger from RR racing is unicorn, I don't think you can even buy one anymore and for $7000, it is more expensive then the IS350. IS350 is obviously just much better choice then, but if track is the target then I would go non-Lexus altogether. Even IS350 is still a luxury car and would require substantial mods (which don't exist and all have to be customer made) before it could go on track.